Waterbom water park in Kuta
A surprising haven of calm amongst the chaos, Waterbom is great because it feels like a little closed in world where you can splash around to your hearts content, away from the hassle on the streets and beach. The rides are a hoot too, including the Superbowl that swirls you round and round and the ever so relaxing Lazy River which needs no explanation.
Visit the markets
You're still in South East Asia so markets are aplenty in Bali. In Kuta there's an Arts market full of lots of wonderful things and potential souvenirs worth a look. Otherwise, there are expansive markets in Ubud with hundreds of different fabrics hanging from the ceiling ready to been turned into a sarong or a scarf or something to sit on to keep your bum dry if that's what's needed. There is of course your usual tat but there's also a lot of great quirky things to be found and inevitably there's food stalls all around too.
Get a Balinese massage
Most hotels will provide a traditional Balinese massage and there are little independent outlets that do it too which are usually cheaper. A Balinese massage is based on applying pressure to key points and there's emphasis on aromatherapy and lots of smelly oils. You wont have your legs yanked behind your head like in Thailand though!
Learn to surf
Bali has some of the best surfing beaches and attracts and influx of surfers to it's waves. These are all situated around the south of the island including Kuta Beach. However this gets very crowed and so you might want to give it a go somewhere a little quieter. There are plenty of surf schools around to choose from too.
Take a cycle tour
A great way to go exploring. As previously mentioned what better way to get around and see the rice paddies in all their glory than cycling around like Julia Roberts on her way to see Javier Bardem (another Eat, Pray, Love reference). Cycle tours are popular or you can rent one and be adventurous going solo.
Cooking classes
Bali and Indonesia are well known for their great cuisine so why not learn how to do it at home from the experts. You can learn to make all sorts of things from Chicken Satay, the famous rice dish Nasi Goreng and supersalad Gado Gado.