Bali Hai Diving Adventures
My fiancee and I dove Nusa Penida with Bali Hai Diving Adventures for 4 days, and stayed at their resort on Nusa Lembongan, the Hai Tide Beach Resort, for 4 nights.
The resort was one of the best dive resorts in Bali, at least from what we saw during our time on the island. There are 2 restaurants serving up tasty food, including great vegetarian fare. We stayed in a nice and clean garden lumbung with air conditioning, a large and comfy bed, and a super easy-to-use mosquito net. It's right on the Mushroom Bay beach, and there are two pools on the grounds for relaxing and having a drink. Staff were all excellent.
It was definitely worth it staying on Nusa Lembongan, which is right next to Nusa Penida, rather than doing the day trip over from the main island of Bali. That cut off 60-90 minutes of boat transportation in each direction, and meant we were the first boat to arrive at manta point in the morning. This is important, because later in the day, manta point gets crowded with boats from Bali.
That brings me to the dive operation, which was extremely well run. The guides were very knowledgeable and safety-conscious, which is exactly what you want when diving Nusa Penida, which is known for its sometimes heavy and unpredictable currents. The dive boat was new and very well equipped, and the staff lug tanks and set up gear for you. Everyone, from the boat captain to the helpers to the DMs, was friendly and helpful.
Most importantly, they provide a high ratio of dive guides to divers. No more than 4 divers for 1 guide, and if the divers have varying skill levels, they may break it down to 1 guide for 2 divers, so as not to pair high air consumption divers with low air consumption divers, for example.
The diving itself was excellent. We drifted over pristine reefs with big schools of fish, checked out giant sponges, enjoyed a lot of time with large turtles (green and hawksbill), got to see an octopus show, and had the best manta encounters I have ever had. Yes, manta point is busy, but it is also huge, and there are lots of big mantas cruising around. When we were there we saw maybe 4 or 5, but we heard that it's not uncommon to see 10-15 on a dive there. And some were 4 m across.
The diving schedule we followed was 2 morning dives, then a return back to the resort for lunch, and then an afternoon dive. For early morning manta dives, we requested the restaurant to pack breakfast for us, which was a nice touch. We did not have to leave that early (7:15 I think) because we were much closer to the site than mainland Bali. The resort/destination is best suited for families, and anyone who wants to spend their topside time relaxing in very nice surroundings, rather than doing long boat rides back and forth from Bali. Sure you can probably save some money on accommodations by staying somewhere cheap on Bali, but that just sounds exhausting to me!
The best time of year for diving Nusa Penida depends on what you are looking for. Mola season is June to October, but the water is also coldest then. Dry season, which is peak tourist season, is May to September. April was great because it was shoulder season...nice weather, great manta and reef diving, but less tourists, so less crowded. October is supposed to be nice because it is also outside of peak season, but has great weather and still has molas. Up to you what you want!