Shetland 536 family four problems

Hi.
I have bought myself a Shetland family four Cracking boat for the price i paid, But went down to the boat yard that i am storing it in and there was about 2 inches of rain water on the cabin floor. Its leaking in from above the cabin, It can't be from the deck area cus that is covered with a waterproof covering. Has anyone had the same problems as me
Thanks for any advice

check all the window seals. first what i would do is put a hose on to the cabin and see where its leaking from

also, if the material cover has any mold, it can act as a barrier for water to pass through. Doesn't sound too serious.

Kev