An abandoned submarine is not likely to remain afloat for what would be now 70 years, IIRC some abandoned ships have managed to remain afloat for several years but not that long and a sub probably has much more potential for leaks. Additionally if one was trying to sneak in somewhere sinking the sub would be a logical move to cover one's own traces, nor a place close enough to civilization to fit the plan likely to remain unvisited for so long. Also while "let's go to Argentina/somewhere" was a popular idea at the end of the war wartime desertion proper was a slightly different matter and not one likely to go down well with an entire crew; not impossible but not likely either.