Staying Warm Underwater
Our colder waters require thick wetsuits (5mm or more) or dry suits. The thicker the wetsuit and the more layers it has, the more hassle it is to put on and take off. Thus, most California divers put their wetsuits on for the first dive and don’t take them completely off until after the last. When choosing your exposure garment, comfort and warmth should be your primary considerations. The fewer the seams the better. Seam location is important, too. Those that run down the back of the legs may cause abrasions at the backs of the knees. If you find a suit you love but it has seams that cause problems, wear a pair of tights, pantyhose or a nylon/lycra skin under.
Dry suit wearers often take their suits partway off or altogether off between dives. Will the one you’re planning to buy be easy to take off and put on? If it isn’t, will you be comfortable wearing it hour after hour? Don’t buy a dry suit until you can answer those questions.
Gloves, Boots and Hoods

Hand protection is a must year-round. Surge, which picks you up and tosses you around, is a way of life here. While mitts are warmer, they greatly limit dexterity, which is why most divers prefer five-finger gloves. These should be thick enough to provide protection from environmental hazards and keep your hands warm. It helps if the palm and finger areas are made of special materials that resist wear and sea urchin spine penetration.

A hood needs, above all, to be comfortable, not interfere with the sealing of your mask and have a skirt long enough to tuck into your wetsuit to reduce water flow—but not so long it bunches up underneath. You’ll need one at least 5mm thick. Watch out for seams that could chafe your neck.

Booties should have sturdy, non-slip soles and be no less than 5mm thick for warmth. Many divers prefer those with zippers because they are easier to put on and take off. A zipper, however, adds bulk and makes it harder to tuck under a wetsuit leg. Zippers also require a bit more maintenance—a freshwater rinse at the end of the trip to prevent corrosion. Before you buy pair of booties, make sure they fit into your fin foot pockets.

Staying Warm Topside
More often than not, the Channel Islands are breezy. If you are going to make multiple dives you need to stay warm between them. The best idea is to wear some kind of windbreaker topside. There are several different models made just for divers. The outside is waterproof, the inside has a fleece lining that wicks water away from your wetsuit. Deep, fleece lined pockets keep your hands warm and toasty.
Although most dive windbreakers have hoods, many divers also bring a hat. A lot of the body’s heat is lost through the head and wearing a hat or hood prevents that.

A hat with a bill or brim also protects you from the sun. Wear a hat and cover exposed skin with a waterproof (and nongreasy, so your mask doesn’t and slide on your face) sunscreen.

Other Accessories & Necessities
Few California divers would consider going into the water without a knife or pair of specially made scissors. Buy a knife that suits your diving in terms of sharpness and size. There are small knives that attach to your BC or console, larger knives that come with a sheath and strap on your leg. You can even have a knife pocket added to your wetsuit.

Snorkels, while considered optional in some parts of the world, are a necessity here. It is easy to swim far from the shore or boat in pursuit of the perfect photo, the biggest bug or any legal sized flatfish. Also, the current can change during a dive. Whatever the reason for it, when you surface too far away to return underwater, you will be glad you have a snorkel for that surface swim.

Fins are a personal choice, but if the straps have extra long ends you should secure them with duct tape. This prevents them from becoming tangled in kelp.

Kelp is also the reason you should streamline your profile, keeping gauges, octopus and other accessories close to your body with clips andretainers/leashes. No one is able to navigate perfectly every dive, if you ever have to swim back to the boat on the surface through a thick kelp canopy you will appreciate being snag free.

Speaking of navigation, a compass is a must for California divers, as is learning to use it. It’s not hard. Take a course or read a book and save yourself a lot of time, trouble, and unnecessary surface swimming. Gear bags, of course are a necessity because California diving is truly gear intensive. Since most of the boats require a walk to reach, gear bags with wheels are great. Many also use backpack gear bags.

Last, but not least, for California boat divers is a sleeping bag. Almost all bunks have vinyl covers. Not only are they cold but bare skin sticks to them. While boats also supply blankets, you usually get only one. You can lie on top of it or under it, but not both. Since a good night’s sleep is essential on a dive trip, a sleeping bag can ensure your comfort. You don’t need one that’s super warm or expensive, even fleece sleeping bag liners will do the job.

Conclusion: These tips are the result of 30 years of California diving; I learned them little by little—but you’re getting them all in one article.