When using a recording depth finder in the open ocean, what phenomena is most likely to produce a continuous trace that may not be from the actual ocean bottom?

Correct Answer: Option D — Echoes from a deep scattering layer

In USCG General Navigation principles (Bowditch, Light Lists, and Coast Pilots), regarding 'When using a recording depth finder in the open ocean, what phenomena is most likely to produce a continuous trace that may not be from the actual ocean bottom', the verified fact is: 'Echoes from a deep scattering layer'.