Hi Max,
How are you?I understand your fearabout the sailing trip and I wil help you.
I think your phobia will dissapear if you start go swimming.It could be a good idea to get used to the sea water.Another idea would be take to swimming lessons By doing this you will get used to water.
I wish your fear dissapear.Write and tell me how you are now.
Talk soon,
Konstadinos