Indy Marathon - Sunday 5/18

[Alex]

Not to mention that in reality pre-WWII diesel submarines could run submerged for only short distances and did their long distance travel surfaced. So staying on wouldn't have been difficult. Even if they had decided to travel all the way there submerged but periscope up they'd have had to resurface about every 60 miles to recharge batteries.

Not being seen by the watch posted outside when surfaced would have been at least as difficult as hanging on in the first place.