rain water in casablanka 31 sailing boat

[gib1970]

I am looking to buy 2005 sailing boat casablanka 31, made of fibre plastic. It has however been left abadoned for 3 years and there is 3foot of rain water in the boat. It is for almost freeto take, but I am worried that both rain and sea watter have damaged core of the boat . Are these fibre plastic ment to survive if left in the sea for over 3 years without paintig and protection and also this amount of rain watter inside the boat? Please someone with similar experience may help. Hope to get this bargain and refurbish inside as long as the shell is ok.