For sure some sort of footwear that you can also wear on the slides.
Even if the ground isn’t hot, it’s better to have traction on slippery pavement.
I believe there are towels in various locations, same as at resort pools, but don’t take my word for it. I always have brought along a towel and kept it with my dry clothes in a locker.
And of course, the shops in TL and BB have a wide range of beachwear and accessories including Mickey themed bath sheets.