To be honest, I felt the Broken Bow section of Rivet City was more difficult( or was that...annoying? ) with regards to swimming (and potentially drowning) than the Oasis area. It got easier the second time around, but the first time through I found myself getting turned around more than once and getting hung up on a submerged shelf or something similar. Plus, those darned Mirelurks that were feasting on me while I was swimming did not help matters.