To save your life learn to sail first. Tacking, jibing, capsizing, righting, different wind strengths...choose a small boat (monohull) that you can easily manhandle both on and off the water. Something like a Sunfish would work well. I have four of them that each cost less than $100 complete. Get to a decent skill level and work through any of your fears (sea monsters and what not) then move on to a cat.

Good luck.