Nobody tells you this before the first dive course: the hardest part is rarely the diving. It is the small stuff around it. The medical form that needs a doctor's signature the day before you start, the mask that leaks because you bought it online, the car key that spends four hours in a damp locker, the phone that gets a salt-water bath on the boat ride back. 🤿 Beginners are not careless. They are simply busy learning buoyancy, hand signals and equalising, and nobody has handed them the list of boring things that go wrong around the water.
This guide is that list. Ten things new divers lose, break or forget during an Open Water style course and the first few holiday dives, with a practical fix for each. It is written for the 2026/27 season, for people who are about to sign up, who are halfway through a course, or who have just been certified and are packing for their first trip. Where a small hard case genuinely helps, we say so, and where it does not (a case is not a dive housing, and it will not fix a bad habit), we say that too.
One note on facts before we start. Courses, agencies and dive centres all run things slightly differently, so treat everything below as general experience and always follow your instructor's briefing and your agency's own rules. Where we give a number, it comes from a published guideline and we name it.
Before the course: paperwork, fit and money
1. The medical form that turns up too late 📋
Almost every recognised course asks you to complete a medical questionnaire before you go in the water. It is a list of yes/no questions about your health, and the rule is simple: if you answer yes to any of them, a doctor has to look at it in relation to diving and sign to confirm you are fit to dive. That is a safety measure, not bureaucracy, and it is not something an instructor can waive on the day.
The classic beginner mistake is to open the form on the morning of the first session, tick a yes about an old asthma inhaler or a recent ear problem, and discover that the next doctor's appointment is in nine days. Do it the other way round. Download or request the form when you book, read it the same evening, and if anything needs a signature, book the appointment immediately. Ask the dive centre whether they accept a local doctor's signature or want it on a specific template, and whether a photo of the signed form is enough.
Then protect the paper. A folded form in a rucksack pocket does not survive a wet boat. Keep the signed form, your passport or ID copy, your insurance details and later your certification card together in one dry place. A small hard case such as the Peli 1060 is large enough for cards and folded papers and keeps them flat and dry through a splashy transfer. Photograph everything as well, and email the photos to yourself so a lost bag is an annoyance rather than a crisis.
2. The mask you bought blind 😶🌫️
A mask is the one piece of kit that almost every instructor will tell you to buy yourself, because fit is personal and a leaking mask ruins a session. The mistake is buying one online because the photo looked good. Mask skirts differ in width and profile, and a mask that suits a friend's face can let in water at the bridge of your nose on yours.
The test is simple and works in any shop. Hold the mask against your face without the strap, breathe in gently through your nose and let go. A well-fitting mask stays on by suction for a few seconds. Check that the frame does not press on your nose or cheekbones, that you can see down toward your fins, and that your moustache or hair is not under the skirt. If you wear glasses, ask about prescription lenses before the course, not after the first failed clearing exercise.
Store it properly too. Salt crystals, sun cream and a hot car shorten the life of a silicone skirt, and a crushed mask in a bag side pocket picks up scratches on the glass. Rinse it in fresh water after every day and keep it in a rigid box rather than loose in a wet kit bag. A mid-size hard case, such as the Peli 1150 or 1200, can serve as a mask-and-accessories box; check the inside dimensions on the product page against your mask before you order.
3. The dive computer nobody has read the manual for ⌚
Many beginners rent a computer for the course and then buy one for the first holiday. Either way, the computer is the most valuable and most fragile thing you will carry, and it fails in unexciting ways. The battery is flat on day one. The settings were changed by the previous renter. A scratched screen turns unreadable in low light. The charging cable is back in the hotel.
Build three habits. First, charge it the night before and check the battery indicator before you leave, not on the boat. Second, learn the display and the alarms in the dry, not at depth, and ask your instructor to show you the settings that matter for your course. Third, never leave it in a pocket with keys or a torch where it can be scratched, and never leave it in direct sun on a dashboard or a boat bench.
A compact hard case is a good home for a computer and its charger between dives. A Peli 1010 or 1020 is small enough to fit a bag side pocket and gives the screen a safe space away from keys and coins. Put a small silica gel sachet inside, and let the computer dry fully before you close the lid after a wet day.
At the dive centre and on the boat
4. The car key that went swimming 🔑
Dive centres are lively, shared spaces. Lockers are damp, bags pile up, and people are in and out of wetsuits all day. The key that was in your shorts pocket ends up in a shared bucket, on a boat bench or, occasionally, in the sea. Modern car keys are especially vulnerable, because a wet key fob can fail or lock you out of the car at the worst moment.
The cheapest solution is a dedicated key habit: one place for the key, always. Many divers leave a spare key with a friend or at the hotel and carry the main one only when they must. If you do carry it to the dive site, protect it. A micro case sized for a key fob, such as the Peli 1010 key case, keeps the fob dry and separate from other metal. Clip it to the inside of your bag, not to your wetsuit, and never put it in a wetsuit pocket on a dive.
Remember what IP67 means here. It describes protection against dust and temporary immersion in a lab test. It is useful for splashes, rain and an accidental drop in shallow water. It is not a dive-rated rating, and a small case is not a replacement for a proper housing or a dry bag, as explained in our article on what IP67 actually means for your Peli.
5. The phone that got a salt-water shower 📱
The phone is the item most often damaged on the way to and from a dive site. It sits in a pocket during a fast boat transfer, a wave comes over the bow, and it gets a mix of spray and salt. Salt is worse than fresh water because it is conductive and corrosive, and it creeps into charging ports and speaker grilles. A phone that survived the splash may fail three days later.
Keep the phone out of your pockets on the boat. Use a small hard case for the transfer, take it out only when you are dry and out of the spray, and rinse the outside of the case, not the phone, with fresh water at the end of the day. A Peli 1020 or 1040 phone case is designed for exactly this kind of use. Check the model against your phone size on the product page, because phones keep getting larger and thicker, especially with a protective cover on.
Do not use your phone as a camera underwater without a proper, rated housing, and do not trust a "waterproof" label for dives. We go through the real options in our guide to the waterproof case or dry bag question, which is worth reading before you buy anything.
6. The paper logbook that turned to pulp 📖
A paper logbook is still part of many courses, and your instructor will sign it. Beginners put it in a rucksack with a wet towel and open it the next day to find the pages stuck together. Ink runs, signatures vanish, and a few months of dives are suddenly very hard to prove, which matters when a dive centre asks about your experience before a deeper trip.
Use a waterproof pen, and write up each dive the same evening while you remember the depth and the conditions. Take a photo of every signed page. Many divers now keep a digital logbook in an app or on the computer as well, but if you keep paper, give it its own dry spot. A flat small case like the Peli 1060 holds a pocket logbook, a pen and your certification card without bending them.
It is also worth keeping a short written note of the practical things you learned that day, such as what weight worked for you or which fin straps slipped. Those notes become your own checklist for the next dive, and a dry notebook is much more useful than a memory.
One more habit pays off over the years: write a short "kit card" and keep it in the same case as the logbook. On it, note your computer model, the date of the last battery change or charge, your mask size or model, the weight you used on your last dive and the names of your instructor and buddy. When a dive centre asks what you dived last time, or when a rental computer turns out to be a different model from the one you trained on, that card saves time and avoids guesswork. It also helps you notice patterns, such as always forgetting the same item, which is exactly the kind of boring information that stops small mistakes from repeating.
Gadgets, chargers and the trip itself
7. The action camera and the card that was never backed up 📷
Almost every beginner wants footage of the first dive. The usual failures are not dramatic floods but dull ones: the memory card is full, the battery is flat, the lens is fogged, or the card is formatted before the video was copied. After a long day nobody wants to sit down with a laptop, so the files stay on the card, and the card stays in a damp bag.
Make the copy a ritual. Back up the same evening, keep the original card until the copy is confirmed, and carry a spare card and battery in a rigid box rather than loose in a pocket. Cards and batteries are small and easy to lose in a dive bag, and a hard case with foam or a few dividers keeps them separate and visible. A Peli 1150 or 1200 is a practical size for a camera, a spare battery, cards and a cleaning cloth. If your camera lives in a housing, flooding is its own risk, which we cover separately in our guide to what survives a capsize and the water-proofing habits that apply to every boat day.
8. Chargers, torches and the power bank problem 🔋
A dive trip means a surprising number of rechargeable items: the computer, the camera, a torch, the phone, a power bank. Beginners pack them as a tangle of cables and discover that half are the wrong connector. The other issue is travel. Spare lithium batteries and power banks are generally required to travel in cabin baggage rather than in the hold, and airlines set their own limits. Check your airline's current rules before you pack, not at the check-in desk.
Keep chargers and cables together in one organised box, labelled by device, with a printed or photographed checklist taped inside the lid. A larger hard case such as the Peli 1400, or a rugged small case such as the Peli Storm iM2100, protects chargers and power banks from the knocks of a dive boat and keeps the terminals covered. Cover the contacts of loose batteries with tape or use the original cases, so metal items such as keys or coins cannot short them.
If you are planning a trip to a new destination, our list of the best diving destinations in Europe shows what the local conditions look like and what to expect from the dive centres there.
9. The wet kit that went mouldy on the way home 🧳
The last day of the course ends with a pile of wet neoprene, a snorkel, fins, a mask and a towel. It all goes into one bag, and the bag goes into a car boot for a four-hour drive or into a suitcase for a flight. By the time it is opened, the kit smells, the zip is stiff with salt and anything electronic in the same bag is damp.
The rule is simple: rinse everything in fresh water, hang it to dry out of direct sun, and pack wet and dry items separately. Wet neoprene and a spare fins bag go in a ventilated bag, and anything electronic, documents, cards and keys go in a hard case that never touches the wet items. A hard case also helps in a car, where a hot boot and damp kit make the perfect mould recipe, and it stops the case contents from being crushed by heavy fins and weights.
Plan a proper wash day when you get home. Rinse the regulator dust cap, soak the mask in fresh water, and let the neoprene dry inside out and then outside. If you are following our dive trip packing list and guide, add a "dry bag for wet kit" line to it, because it is the item most often forgotten.
A practical tip for road trips: never leave the case with electronics in a parked car in summer sun or in a freezing boot overnight. Heat and cold both shorten battery life, and condensation forms when a cold case is opened in a warm room. Let the case warm up to room temperature before you open it, and the contents will stay dry. The same applies at the end of a cold-water course in autumn or winter, when kit comes out of a freezing boot straight into a heated hotel room.
10. Flying home too soon ✈️
The most serious mistake on the list is not a lost item. It is planning a flight too close to your last dive. Flying reduces the cabin pressure, and the nitrogen still in your tissues after diving can form bubbles at lower pressure. The widely quoted consensus guidelines from the 2002 Flying After Diving Workshop suggest a minimum surface interval of 12 hours before flying after a single no-decompression dive, and 18 hours after multiple dives per day or several days of diving. The same guidance stresses that these intervals do not guarantee that decompression sickness cannot happen, and that longer is safer. For decompression dives, the guidance points to an even longer interval.
Many dive computers show a "no-fly" countdown, and some agencies and dive centres use stricter figures, such as a full day. Follow the most conservative number you are given, and book your flight so that the last dive is well before the interval, not just on the edge of it. On a course, where days are tightly packed, the sensible plan is to leave the final morning free and to schedule the last dive the day before you travel at the latest.
When you pack for the flight, keep your computer, certification card and medical papers in your cabin bag, in a case that cannot be crushed. Do not put the computer in a pocket with your phone and keys during security screening, and keep it charged until you are home so you can still read the no-fly countdown.
Small cases for the things that must stay dry on the boat and the beach
Bigger boxes for the camera, the chargers and the whole dive-trip kit
Your pre-course checklist
Print this or save it on your phone. It takes five minutes to run through the night before your first session, and it covers the ten problems above.
- Medical form completed, doctor's signature obtained if any answer was yes, photo of the signed form saved.
- Passport or ID, insurance details and certification paperwork in one dry case, with photo copies emailed to yourself.
- Mask tried on in a shop, strap adjusted, stored in a rigid box.
- Dive computer charged, settings checked, charger packed, screen protected.
- Car key left safe, or carried in its own small case, never in a wetsuit pocket.
- Phone in a small hard case for the boat transfer, not in a pocket.
- Waterproof pen, logbook and certification card together, with photos of signed pages.
- Camera cards backed up, spare card and battery in a box.
- Chargers, cables and power bank labelled, with spare lithium batteries planned for cabin baggage.
- Wet and dry kit packed separately, flight booked outside the no-fly interval.
Frequently asked questions
Do I need to buy my own dive computer for the course?
Not necessarily. Many dive centres include rental equipment in the course price or offer it for a small fee, and instructors often recommend waiting until you have done a few dives and know what you want from a computer. If you buy one, practise with it in the dry first and check the manual for the no-fly countdown.
Is a Peli micro case a dive housing?
No. A micro case such as the Peli 1010, 1020, 1040 or 1060 is a watertight transport case, with IP67 protection against dust and temporary immersion. It is made for keeping phones, keys, cards and small electronics dry on boats, beaches and in bags. It is not intended to be taken underwater as a camera or phone housing, and it is not tested for dive depths.
How long should I wait before flying after my course?
Consensus guidelines from the 2002 Flying After Diving Workshop suggest a minimum of 12 hours after a single no-decompression dive and 18 hours after repetitive or multi-day diving, and longer is safer. Some agencies and computers use a more conservative figure, so follow the strictest number you are given and plan your flight accordingly.
What should I carry in my cabin bag when I fly to a dive course?
Your medical papers, ID, certification card, dive computer, camera, chargers and any spare lithium batteries or power banks, because airlines generally require these in cabin baggage. Check your airline's current rules, and pack fragile electronics in a hard case so they are not crushed by other items.
Where should I keep my phone on a dive boat?
In a small hard case in your own bag, away from the edge of the boat and out of the spray. Avoid wetsuit and shorts pockets, because they get soaked and salty. Rinse the outside of the case with fresh water at the end of the day and let it dry with the lid open.
Should I take a course in autumn or winter?
Many people do, especially in warm-water destinations or in heated pools followed by a holiday trip for the open water sessions. In cold European water, expect thicker exposure protection, more kit to carry and slower, colder transfers, so every item on this list matters a little more. Wet gloves, a hood and a thick suit mean more damp bags, and cold batteries drain faster, so keep spares in an inside pocket and charged devices in a case close to your body until you need them.
What is the single most useful thing to bring that beginners forget?
A small, clearly labelled dry place for the things that cannot get wet, such as the key, the phone, the cards and the computer. Almost every problem in this article comes down to important small items being loose in a damp environment. One organised hard case, kept in the same bag pocket every time, solves most of it.
One last thing
A dive course is a lot of new information in a short time, and it is completely normal to lose a key, flood a phone or forget a charger along the way. The point of this list is not to make the trip stressful but to take the small, avoidable problems off your plate so you can concentrate on the thing you came for: learning to be calm and comfortable underwater. Pack the paperwork, protect the electronics, respect the surface interval before you fly, and enjoy your first real breath underwater. 🤿
