What kind of paint or varnish is used to protect ships from water?

Answer 1

Copper based.

Answer 2

Above, or below the waterline?

Above, to protect from spray, oil or synthetic based treatments - these days, very often urethane based,

Below the waterline, anti-fouling paint... which is really just a slow-dissolving poison, intended to kill off any marine growth that tries to make its home on the hull.
Traditionally, heavy metal poisons are used, copper, arsenic, etc. A little while ago, there was a sudden rush of concern about all that heavy metal being dumped in the sea, so there was a brief love affair with things like Tri-butyl Tin, which turned out to be even more harmful to the environment, so most people went back to doing it the old-fashioned way.

Check with your local environmental control authority to find out what's permitted

Answer 3

It depends on the type of material. Alluminum would require one type of primer and paint, steel another, fiberglass another, and wood another. Also, a lot of navies sometimes use a special radar absorbing paint. Most steel hulled boats can use a marine enamel, or environmental rules permitting, lead based paint.
Proper application also, plays a role in how effective the paint will be. Steel surfaces for example, should be cleaned, dried, and have rust grinded down. They should then put two coats of primer and two to three coats of paint on to make sure that the job lasts.

Answer 4

being I am an x navy man we used a urethane type based paint. However, that is for a steel hulled ship. Fibreglass use the same basic scenario but more of a hardener base.

Answer 5

well it is OIL paint mainly
because it does not absorb water and maintains the ship to last long.
it is not only the paint but the wood used too is supposed to be water proof one such eg. is Sundari trees (found in India, near sundarbans where the largest delta in the world is found)