Sinking Ship Effect Caused by Ocean Swells

It has been determined that, at times, the sinking ship can be caused by the swells on the water between the observer and the target body.

Sinking Bascule
The following image was provided to us:



Thork says:

Ski says:

On The Dimensions of Ocean Waves
In Earth Not a Globe its author provides a citation from "On the Dimensions of Ocean Waves" by Admiral Coupvent de Bois: