Here's a few relevant references:

Romanenko EV. Swimming of dolphins: experiments and modelling.
Symp Soc Exp Biol. 1995;49:21-33.

Videler JJ. Body surface adaptations to boundary-layer dynamics.
Symp Soc Exp Biol. 1995;49:1-20

Anderson EJ, McGillis WR, Grosenbaugh MA. The boundary layer of swimming
fish. J Exp Biol. 2001 Jan;204(Pt 1):81-102.

The last one has a lot of data and I was able to access it
electronically- I can email it to you if needed. They give a drag
coefficient of about 0.01, but there's a lot of detail I skipped over.
Also try Lighthill's classic "Mathematical Biofluiddynamics" text.

For the second question, I assume you are asking for the (solid body)
cross section that produces the lowest drag coefficient? If so, that's
all over the place:

Glowinski, R. and Pironneau, O. On the numerical computation of
minimum-drag profile in laminar flow. J. Fluid Mech., 1975, 72,
385-389 Part 2.

Pironneau, O. On optimum profiles in stokes flow. J. Fluid Mechanics,
1973, 59, 117-128 Part 1.

Huan, J.C. and Modi, V. Design of minimum drag bodies in
incompressible laminar flow. Inverse Probl. Eng., 1996, 3, 233-260.

Solution to shape optimization problems of viscous flow fields
EIJI KATAMINE=86*, HIDEYUKI AZEGAMI=87, TOMOYUKI TSUBATA=A7 and SHOJI ITOH
International Journal of Computational Fluid Dynamics, Vol. 19, No. 1,
January 2005, 45-51

Shaping of axisymmetric bodies for minimum drag in incompressible flow
PARSONS, J.S. (Purdue Univ., Lafayette, IN);GOODSON, R.E.(Purdue Univ.,
Lafayette, IN);GOLDSCHMIED, F.R. Journal of Hydronautics 1974
0022-1716 vol.8 no.3 (100-107)

Unfortunately, none of those are available electronically (to me).
--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University