I had bought a set of the mirage oasis mk11 for my deck, I just opened them and they say do not directly expose to sun or rain. Of course I want to put them out on my deck, facing South and exposed to the rain. I live in Massachusetts, US. Looking at your setup, it looks like your speakers are exposed to sun and rain :-) Have they held up for you?
Nice set-up. It is so fun to float in a pool and hear good quality tunes! I moved my pool-side speakers to "ear" level from the pool or lounge chair (about 2' off the deck) and it improved the sound even more. Cool stuff. Happy swimming!