We purchased the Aquaventure Super Pass on their website which includes the Lost Chambers Aquarium. We also purchased access to one regular size locker which held our small backpack.
Be sure to get there as soon as the park opens (9:45 am)
to avoid the long lines. When you get in, go first to the Guest Services Kiosk. Ask for the free AquaSox, then get the wristbands for the slides. The wristband also opens the locker. The lockers/changing rooms/ showers are just to the left of the Kiosk.
Be sure to get a map. This is one of the worst signposted parks I have ever been to!
We started at Neptune Tower and did all of the raft rides as well as the Leap of Faith twice!
We also did all the group and single raft rides at the Poseidon and Trident Towers. But the pavement gets really hot even with AquaSox. We found a solution to getting between the lockers and the other two towers. There is a golf cart transportation system between the two parts of the Atlantis hotel with stops in between at all 3 towers. Just ask an employee where the nearest stop is. This allowed us to go the lockers for snacks and water and back without much walking in direct sun.
Though the Lost Chambers Aquarium was small compared to the Dubai Aquarium, we felt it was worth the extra $10 per person, the exhibits and big viewing room were beautiful, and it was air-conditioned. This allowed us to cool down and rehydrate before heading back to the hotel.
If you are in Dubai and have some time, don't hesitate!