Gear: what coastal water actually demands
Coastal paddling asks different things of kit than inland paddling: salt, cold, distance from help and a water state that can change within an hour. This is what that changes.
The boat
A sea kayak with bulkheads at both ends and a reliable skeg or rudder is the baseline for anything on this site. Bulkheads give you a boat that still floats when a hatch fails; the skeg lets you trim the boat rather than fight it when the wind comes from the side. Length is a matter of taste, but a 16 to 18 foot boat handles the chop in a tidal passage noticeably better than a short play boat.
Two features worth prioritising over everything else for coastal work: deck lines that run the full length of the boat and are actually rigged under tension, and a day hatch you can open while seated. Both are about staying in the boat and out of the water.
What you wear
Dress for the water, not the air. A dry suit when the water is under 15 degrees, a well-fitting wetsuit or a two-piece immersion suit above it. A spraydeck that you can release by feel, not by looking. A buoyancy aid rated for a person, worn done up, not stowed.
Gloves or pogies in cold water, because cold hands end rescues before the swimmer does. A hat that stays on in wind. Sun protection that is not optional even under cloud, because the reflection off water is unforgiving. And a spare layer in a dry bag, because the difference between a good day and a hypothermia risk is often one dry fleece.
Navigation and communication
A deck-mounted compass that you can actually read while moving, and a chart or chart app that covers the whole of the water you might end up in rather than the water you intended to paddle. In a tidal passage with land on both sides it is the easy place to relax, and that is exactly where people end up two miles from where they thought.
A VHF radio with DSC, registered, on your person rather than in a hatch, because a radio in a hatch is a radio you cannot reach when you are in the water. Channel 16 monitored. A phone in a waterproof case as a second means, and a personal locator beacon for anything remote. In cold water and a running stream, being able to call for help from where you are is worth more than every other item on this page.