What to wear on the water: foul-weather jackets and trousers, deck shoes and boots, the layering that keeps a watch warm at night, and the sun protection that matters more than any of it in summer.
Dress for the wind and the water you will be on, not the forecast ashore: it is reliably 5 degrees colder on the boat, and wetter. Wear three layers you can add or remove: a synthetic or merino base layer that wicks, a fleece or light insulated mid layer, and a windproof, waterproof shell. Closed-toe shoes with non-marking soles, a hat with a strap, polarised sunglasses on a retainer, and a lifejacket over everything. No cotton and no flip-flops on deck.
Why is cotton bad for sailing and boating?
Cotton absorbs many times its own weight in water and holds it against your skin, where it conducts heat away far faster than dry fabric does. On a boat it gets wet from spray, rain or sweat and then never dries in the breeze, so a cotton T-shirt and jeans turn into a cold compress that lasts all day. Synthetic fabrics and merino wool wick moisture outwards and keep insulating when damp. On a hot, dry powerboat afternoon cotton is merely uncomfortable; on a cool sail it is a hypothermia risk.
What are the best shoes for boating?
Closed-toe shoes with soft, non-marking, siped soles that grip wet fibreglass and do not leave black streaks on the deck: proper deck shoes, sailing trainers or water shoes with a real sole. Flip-flops are banned on many boats because they slide on wet decks, fly off, and leave your toes exposed to cleats, chain and dropped gear. For cold or wet conditions, sea boots with the same non-marking sole, sized to take a thick sock and to come off if you end up in the water.