How can I stop the water overlapping the landscape?

I have a flat landscape as an island, I want the ocean to surround it but the water comes through the ground, what is the best way to avoid this?

If there is an easier way to create an island with the ocean surrounding it then please advise me :slight_smile:

Thanks.

Giving some height to the landscape and creating โ€œbeachesโ€ with slightly lower Z world location
try to use the flatten tool it really helps in this kind of situation