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Old 05-08-2012, 04:20 AM
DSeid DSeid is offline
Join Date: Sep 2001
Location: Chicago, IL
Posts: 19,434
Dolphins have a propulsive efficiency of 0.81. Not sure what propulsive efficiency subs have.

If you want a detailed explanation of the differences between swimming modes in fish read this. Short version pertinent to the op:
Thunniform mode is the most efficient locomotion mode
evolved in the aquatic environment, where thrust is generated
by the lift-based method, allowing high cruising speeds to be
maintained for long periods. It is considered a culminating
point in the evolution of swimming designs, as it is found
among varied groups of vertebrates (teleost fish, sharks, and
marine mammals) that have each evolved under different
circumstances. In teleost fish, thunniform mode is encountered
in scombrids, such as the tuna and the mackerel. Significant
lateral movements occur only at the caudal fin (that produces
more than 90% of the thrust) and at the area near the narrow
peduncle. The body is well streamlined to significantly reduce
pressure drag, while the caudal fin is stiff and high, with a
crescent-moon shape often referred to as lunate [Fig. 7(d)].
Despite the power of the caudal thrusts, the body shape and
mass distribution ensure that the recoil forces are effectively
minimized and very little sideslipping is induced. The design
of thunniform swimmers is optimized for high-speed swimming in calm waters and is not well-suited to other actions such
as slow swimming, turning maneuvers, and rapid acceleration
from stationary and turbulent water (streams, tidal rips, etc.)