I cant help with swimwear recommendations, but I would encourage you to swim.
I have for the past 7 years swum 2.5 kms most mornings. I'm sure it helped massively with my continence (dry from day one) and my overall recovery.
However, as a measure of the RRP impact, pre-op I could swim 2.5 kms in 50mins, I took me months to get below an hour and at the moment i.e. nearly 8 months post-op, approx 56 mins, so still 12% - 15% slower!
I have also made lots of friends at the pool, including 2 other PCa sufferers.
Get wet in a good way!! ;-))