We always rent a locker at the water park. We've never had an issue. The locker system is very simple, and you can go in and out of the locker as many times as you need. I'm trying to recall, but I think it was only around $10 to rent a large locker (can store a backpack in it) for the day. They also have a smaller, less expensive option. It's all digital now, so you enter your own code for access - no need to carry a key or anything.

It's really a matter of what you feel more comfortable doing, and if you'd like to bring some things with you that you want to protect, but access during the day.

Enjoy! It's a fun place to spend the day!