[jonathanp88]

You are thinking of nuclear submarines.

Submarines of this era would have a bank of batteries, using 1940's technology, which they could use to run the boat whilst submerged. Once they were flat, they would have to stay at or near the surface long enough to charge them again(they could run at the surface using a 'snorkel' to bring in air for the engines.

They would submerge only to attack or to hide. So looking at it from a range perspective is perhaps not the best way. They could have stayed submerged under water for a long time, but they couldn't be cruising flat out whilst doing it.

[PhasmaFelis]

Which explains the shapes of submarines in the two eras: they're optimized for their preferred mode of operation. Diesel submarines were shaped approximately like a regular ship, with a angled and tapered prow to cut the waves. Nuclear subs are shaped like a torpedo, roughly cylindrical with a rounded prow, to move through deep water.

[brandmeyer]

The shift in thinking about submarine hulls occurred at about the same time as changes in propulsion, but they were separate developments. USS Albacore was the first to prototype the hull shape. A short-run class of diesel-electrics were designed to that shape before being completely overtaken by nuclear propulsion in the US.

All modern submarines, including AIP, diesel-electric, and nuclear, use hull forms optimized for underwater operations.

[rtkwe]

There are some neat ones employed by Sweden that use Sterling engines powered by liquid oxygen and diesel which is pretty neat and makes them really quiet.

[rtkwe]

And later in the war radar made even the semi submerged operation via snorkel pretty dangerous because the snorkels would show up on radar. If they were discovered while doing that they'd be at a pretty stark disadvantage because they wouldn't have a full set of batteries to submerge and avoid the submarine hunters.