Sunken items in the water

[MortThe2nd]

Unless manually put there, the sim does not currently model small boats/piers/marinas.
There’s a wishlist item;

Wishlist item for Blackshark AI: marinas, piers and small (sail) boats - Self-Service / Wishlist - Microsoft Flight Simulator Forums

Only in photogrammetry areas you’ll see some shape to them as @TheSevenflyer mentions.