We booked a morning snorkel trip to Molokini and our first attempt was thwarted by high winds , rough seas, and a small craft advisory against going. Our choice was to go to selected spots around Maui, or to rebook, which we chose.
Fortunately our second booking went well and the Ocean Voyager one of the first out there which was great. The crew were very helpful, informative and safety conscious at all times. The water was unbelievably clear and it was a great experience.
We then went to turtle town, sadly saw no turtles, but plenty of fish. We also got to see whales!! We had seen their waterspouts in the distance on our way back in from Molokini, but got a closer view of them after our second snorkelling. That really made our day. And the crew were full of interesting facts and information while we watched, they were always happy to answer our questions, chat about marine life, pollution issues etc.
The only downside was really with our initial experience. It was not very clear where we were to meet for our trip - the store - but there was a sign for Whale Watching Tours and nothing else. Loads of people milling around and just 3 or 4 clipboards with waiver forms for everyone that had not wanted to do it online. It also seemed very disorganized when dealing with either rebooking or cancelling, yet this must happen fairly regularly. Having said that, everyone was very polite and helpful under pressure.
So if you want to visit Molokini, allow for weather to change your plans, try not to book the day before you leave, and I imagine that the 7am trip generally has calmer water too.