V wakes

[Mr. Sandman]

Not to sound like a wise ass but from a hydrodynamic standpoint just about anything moving beneath the free surface leaves a wake...has to. Even at very deep depths...the waves may be so small or masked by wind-generated waves so you can't visually pick them out but they are there. As a body gets closer to the free surface the waves become larger in amplitude and more visible. Wave generation is primarily a function of vessel speed and depth below free surface. When the body is within a couple diameters of the free surface it causes significant forces on the body below making it difficult to maintain a near surface depth without active control (fish are good at this).
Below is an image of a simulation I did of a submerged spheroid at a Froude number (a non-dim speed number) of 0.6 and depth to Length ratio of .245. The colors are wave height above (blue) or below (purple) the mean free surface.

End of today’s hydro lesson...