Well no, flip-flops would certainly be fine hanging out by the pool.
The pool deck is used for lots of parties, and they are very informal. But there also isn't much shade out there, so lolling in a lounger becomes problematic--the sun is very strong. And the pool is *very* small. Last time I was there, it was Easter, and the pool was full of children. Also, dive lessons happen in the pool the first day or two.
And of course, you have your balcony, you lucky guys! We dropped down to a window cabin some time ago (and held on to the b2b instead.)
I will be chasing shade whenever I can, which can mean roaming around the ship as it twists around at anchor!