Crystal Bay

Crystal Bay is a reef dive site on the west side of Nusa Penida, Bali, Indonesia, reached by boat from Sanur via speedboat across to the island. The bay is well known for its clear water and serves as one of the primary locations in Bali where Mola Mola (ocean sunfish) are reliably encountered. At Crystal Bay, the Mola Mola use the bay as a cleaning station, where they can be seen waiting patiently while being cleaned by schools of Bannerfish; they are also occasionally spotted lying on their sides at the surface basking before descending. The site reaches a maximum depth of 40 m, with the Mola Mola typically appearing at depths between 18 m and 40 m.

The prime season for Mola Mola sightings runs from late July to early November, with peak encounters in August and September, coinciding with a seasonal drop in water temperature. During the Mola Mola season, water temperatures can fall to 15–16°C, and thermoclines are common, bringing rapid temperature drops at depth; outside this period temperatures are generally in the low 20s°C. Visibility is generally excellent, in keeping with the bay's reputation for crystal-clear water.

Conditions at Crystal Bay are demanding. The site is exposed to strong and unpredictable currents from the channel, and strong down currents are present near the deeper sections. Access is weather, tide, and swell dependent, and the calmest dives are achieved at slack tide. Thermoclines and cold water add further challenge. Because of these conditions, an Advanced diver certification is required; the site is not suitable for beginners.