As an additional data point, the fact that a water based mucous should
have basically an identical electron orbital period to seawater
(assuming whatever is dissolved in the water to turn it into a mucous
doesn’t alter the base water’s orbital period), coating either the
submarine or the dolphin in that mucous would result in a reduction in
turbulence simply because the two layers of material would have
identical orbital periods resulting in a much reduced opportunity for
inertia and other factors to force the two material faces into an overly
close proximity of each other, reducing the possibly of a rebound
reaction. I would check the dolphin to see if its skin secretes a
mucous, and you could try replicating that mucous if it exists and put
in on a steel hull to see if it works.