LAG.. too many ships on the bottom??

[Hanomag]

Recently I have been goofing around.. I found a "sweet spot" for VonDos's SS Normandie and USS West Point as well as GWX standard 24k ton Troop Ship. As kind of a joke between me and a friend I have been trying to see how many times I can sink them each and whats the highest tonnage I can achieve.

I am wondering if in the shallow area I am in (200m-300m) is not deep enough for the behemoth VD ships to despawn?

I am getting a tremendous amount of lag. (normally I experience zero lag)With 4 Normandies and 4 West points on the bottom under my boat, even when reloading a save in the same spot. Alot of lag at first then it slowly goes away. It actually caused instability and CTD so I had to end my last patrol with a paultry 457k tons.

Anyways just curious about the whole despawning sunken ships thing..