Basically, nothing much. But there are few leisure activities you could consider.
First, wake up early in the morning to view the sunrise.
You gotta be patient to call the shy sun out to meet you :D
You could just cycle from one end to another end, not easy if you pass by sandy area.
Third, you could do snorkeling. Else you could decide for a more challenging one - diving.
If you don't have a license, you could take the course and be learnt in few hours.
Fourth, on fine-weather day, you could see people surfing.
You could sit on the beach bar, enjoy your drink and the surfing.
While doing so, you could also enjoy the breeze whispering around you.
Sixth, you could go for a free movie by ordering beverage or food valued Rp25,000. The cinema is cool and unique whereby you could choose to lying down or sitting.