Yakov Winer asked:
what is the Mechitzah?? the water or the wall of the sea?
The Kollel replies:
The wall is the Mechitzah. If it is not ten Tefachim at the shore it must at least be a Tel ha'Mislaket (an incline with a ratio of ten Tefachim height within four Amos distance).
D. Zupnik