Water flow in offshore waves

What happens in the crests of large, steep waves? Circumstantial evidence from the offshore engineering industry points to much higher flow speeds than predicted by the Stokes model, but definitive measurements allowing careful comparison with the theory are generally lacking. Near-surface velocity measurements at higher sea states are notoriously difficult to acquire, motivating development of innovative instrumentation. Recent observations with under-water acoustic sensors indeed show that surface flow speeds can differ from theoretical expectations, especially in wave crests.

We used a method of acoustical remote sensing that bears some similarity to bistatic radar measurement …