There are lockers available for hire, go to the back of the park beneath the slides on the right, go down some stairs where the toilets are and you will find them there.
I don't know where your
hotel is as you haven't said where you are staying so can't help on that one.
The park is busy in the morning easing off in the afternoon so less queues for the slides.
Last year we got the water taxi in the morning to Marmaris, had a look round the castle, a gentle stroll down the prom and stopped for lunch, we then went in the park at 13:30 when they switched the slides back on after a stoppage for lunch. Left the park about 17:00 and caught a taxi back to Icmeler.
Dave