Way too crowded. If you don't get there early enough to secure a lounger in the front rows you are then forced to have loungers in front and behind you with barely enough room to navigate in and out. The loungers on either side of you are right next to you without ANY space to get your bag between. It's awful.
There is a sign at the entrance of the pool which states that if you have not been in your lounger for an hour or more it's free game for anyone. We witnessed a little argument with a person who had been gone for over two hours so a couple took their loungers. She was not nice; even though she was in the wrong.
The Oasis pool is for 21+ and well worth the $55 I paid on the last day. There is not a bad seat there and staff brings you an occasional freebie like cherry lemonades, fresh sliced pineapple. It was nice to be able to sit under the umbrella and move out into the sun whenever I wanted without having to figure the best way out. If you stay at the Mirage pay the extra for a reserved lounger at the Oasis pool.
Reserve it at the concierge desk.