As a general rule, thicker neoprene insulates more, so colder water pushes you toward thicker accessories, but fit, dive length, and personal cold tolerance matter as much as the millimeter number. Divers commonly lose a great deal of heat through the head, so a hood is often the highest-value warmth upgrade for the money. Remember that every added piece of neoprene also adds buoyancy you will need to account for.

Boots should fit like a snug athletic shoe, with no heel lift and no crushed toes; a little water inside is normal, a sloshing pocket is not. Try them on with the socks you would actually dive, and remember your fin foot pocket has to accommodate the boot. Hard-sole boots protect on rocky shore entries, while soft-sole boots are lighter and pack smaller for boat and travel diving.

Gloves should be snug across the palm with fingertips reaching the ends without bunching, since trapped air and loose fingertips destroy dexterity. Thicker gloves are warmer but make buckles, clips, and inflator buttons harder to operate, so choose the thinnest glove that keeps you comfortable in your conditions. Try working a clip or buckle while wearing them before you commit.

A hood should seal around the face and neck without restricting your throat or jaw, and lie flat on your head without pulling the mask strap out of position. A loose hood flushes cold water continuously, while an overly tight one is distracting and uncomfortable. Many hoods have a vent to release air trapped during descent, so check yours and burp out any trapped air before you go down.

New neoprene compresses and relaxes with use, so a boot, glove, or hood that feels firm out of the packaging usually settles slightly after a few dives. It should still be snug afterward rather than loose, because neoprene that stretches into a loose fit was probably oversized to begin with. Buy for a snug fit when new, but never for a fit that restricts circulation or breathing.

Yes, because every piece of neoprene you add is buoyancy, and a hood, boots, and thick gloves together can shift your weighting noticeably. Do a proper buoyancy check any time you change your exposure protection rather than assuming your usual weight still works. The weight-check procedure is covered in your training, and a dive professional can help you re-do it.

Rinse them inside and out in fresh water after every dive day, since they hold sweat and salt more than any other gear, and dry them fully inside-out before packing. Dry them out of direct sunlight and never on a heater, because heat hardens neoprene and weakens glued seams. Store them dry and unfolded, as damp neoprene sealed in a bag is how gear picks up a permanent smell.