Steven Spielberg at one point was heavily involved in making a movie based on Admiral Fluckey's book "Thunder Below" was put on the shelf due to the fact that Universal was developing (the crappy) U-571 at the same time.
from Yahoo movies on writer Shane Salerno...
"Schmidt was also pitching a submarine story, "Thunder Below" which Salerno convinced Schmidt to let him write. Both projects were ultimately stalled, but not before "A Season in Hell" was bought for mid-six figures and "Thunder Below" was greenlighted by Steven Spielberg for DreamWorks. "
And just to show how many movies get knocked back check
this feature from the UK Independent newspaper from 1998 which includes Thunder Below, I think the only movie made on the list was the then titled Proteus which became "Below. It's a shame as it was probably the worst of the bunch listed, but that's Hollywood!
Let's hope Mr Spielberg "unshelves" the film someday as WWII American submariners certainly deserve a serious movie of "Das Boot" quality as a tribute to their heroic exploits.
***UPDATE***
Whilst Steven Spielberg has not taken Thunder Below down from the shelf yet he has announced literally hours ago a new 10 part "Band of Brothers" style series called
"The Pacific" following the wartime experiences of three American GIs.