death of relative

[clang]

Im trying to trace details of the death of a distant cousin who died in the second world war. Family story says he was on a submarine being tested which did not come up but I realise this is a story relatives were often told. His name was James E Brown and he was known as Jim. He was born in 1921 and I think he died about 1940 so he would have been 19. Unfortunately the only 2 living relatives that remember him are unable to help more although one says she doesnt think he was in the Navy.That I think will be incorrect unless he worked for the shipbuilders. I have tried the submarine museum with no luck and have looked at all Brown deaths between 1939 and 1942 and none look right. I also realise that the time is within the 100 years so not all info may be accessible. Can anyone help with other sources etc. thanks
P.S. Im new to this messaging lark so hope Im doing it right