For snorkelling and diving, the closest spots to Kuta are Benoa and Sanur beaches where all the relevant equipment can be hired. Further afield, good destinations include Pulau Serangan, Nusa Penida an Nusa Lembongan in the south, Padang Bai, Candidasa, Tulamben and Amed in the east, Lovina, in the north and the amazing Pulau Menjangan in the north west. A number of dive courses are available with different companies including PADI, CMAS and SSI certificates.
Bali's waves are world famous and range from safe beach breaks for beginners like Kuta to the awesome swells at Padang Padang, Uluwatu and Nusa Lembongan, which regularly attract the pros. If you want to learn, boards can easily be rented for a negotiable fee or take a lesson at Bali Learn to Surf (761869).
Beginners should respect the sea and stay within depth to start with as the current can be very strong. Apart from Kuta and Legian beaches, Medewi is also good for beginners. For the more experienced, Nusa Dua has a number of breaks as does Sanur, Canggu, Ketewel and the area around the airport are also popular with experienced surfers.
For information about tides etc there are two main surfer's bars: Tubes in Poppies 2 and the All Stars Cafe in the Kuta Centre.