HI, when you rent a locker, they also have towel rentals there as well! This is from the Aquatica website......
Amenities
•Dining facilities throughout the park offer a variety of delights
◦Aquatica has several different dining options including an all-you-can-eat restaurant and healthy alternatives.
•Gift shops feature a wide selection of brand-name sportswear, beachwear and other "must-have" summer items.
•Beach and picnic areas
•Showers, changing areas, and nursing mother's station
•A one-time locker fee gives you a full day's worth of unlimited access. Small lockers are $5* and large lockers are $10* per day.
*All locker rentals require an additional $5 refundable key deposit
•Beach towels can be rented for the entire day for a $4.00 each. Towels can also be purchased at any of our shops throughout the park. •Life vests can be checked out free of charge throughout the park.
Hope that helps! That being said, we actually bought some 2/$10 at Walgreens and washed them at the resort the night before! Only problem was, we had a hard time fitting 4 beach towels in our suitcases on the way home!