There is a great beach in Bali, at Nusa Dua, as good as any beach in Thai or elsewhere. Its called Pantai Mengiat, and it fronts the Grand Hyatt, Ayodya, and St Regis Hotels, and hosts the beach club for the Amanusa.
The beach is protected by an offshore reef, which prevents waves from breaking on the beach, thus keep the water calm and easily swimmable. Surfers ride boats out to the reef to surf.
The beach can be accessed easily, without staying in the hotels. There is a free parking lot for the cafe there run by the local village cooperative called Yasa Segara. The cafe rents beach chairs for about 20,000 rps/day, has showers, restrooms, and has a pretty good F&B menu. Some local fishermen operate from this beach as well.
Further down the beach, towards Geger Temple and Nikko Hotel, is the Geger beach cafe, run by a local village. It also hosts The Bale Hotel beach club. This beach is popular with local Bali expats, has a nice cafe and rents beach chairs. Whether is legal or not, this beach is tolerant of topless sunbathing. The parking lot charges a small fee.
Pantai Mengiat is not the best for snorkeling - its mostly sand. There is a snorkel spot on the other side of the "north and south" islands (small lava rock formations that separate Pantai Mengiat from the beach fronting the Westin, Conrad etc hotels) in front of the Westin Hotel area. Glass bottom boats frequent this area.
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