I'd be careful trying to swim very far off and ocean shore. I was
surprized once while swimming in the surf how far the undertow(?)
carried me away. I had to swim hard to get back to the beach. Dumb
tourist.

I'm a freshwater boater myself but I've read that a boat rising and
falling on ocean swells can drag it's anchor if the line is too short.
When a storm hit our exposed moorings at a local freshwater sailing
club a lot of boats dragged their moorings and those were large
concrete blocks.