Because submarines are designed to be "streamlined" in the first place? Such that anything that wasn't so designed would not meet the definition of "submarine," and thus would not be in the Naval Warfare Museum in the first place? For it wouldn't even qualify as a "submarine?"
The "spotty" fossil record seems to be of no help to you here, allmendream. One could crudely say that the fossil record is a crap shoot (by your own admission) in the service of the defense of another crap shoot (biological speciation as a random walk).
And yet it seems you inadvertently may have stumbled into the periphery of design theory here. Be careful!
Then again, what is the meaning of your comparison of the Naval Warfare Museum to natural selection? There's nothing "random" about a Naval Warfare Museum....