The boat ride across the strait from Sanur, Bali to Manta Point can be a bit choppy, however once you get there it is well worth it. Even if you leave early in the morning there will be tons of diver and snorkelers, however the good news is everyone says it is almost guaranteed you will see Manta Rays. We saw several Mantas plus much more that day. Visibility was about 20-25M. The water temp was around 25C that day, so a 3mm shorty is a good idea. There's some current and surge, so that can make getting back on the boat a little challenging. Great dive and worth the trip.