My wife booked this well in advance of our trip to Hawaii based on reviews. Our first time in Hawaii. I don't like all negative reviews and think a lot of the positive ones must be from very type A people. So, I thought I'd offer up my experience from a land-legged, type B perspective.
The staff did a good job providing food and drinks to those who wanted it. They were all very nice and knowledgeable.
Unfortunately the day we went, the seas were quite rough. The boat was packed full. My family of four was unable to sit together and we were about in the middle of the pack when getting on. We had to rudely force people to make room to allow me and my 11 year old to sit together. My wife and son were spread out and unable to get the staff to accommodate. The packed boat was really really clostraphobic. It was hip to hip, no place to put stuff (backpack with towel, sunblock, sandals) other than really close to the holes in the boat or edge. And, they continued to hand you things to hold (snorkel, mask, flippers, wetsuit, food). The one thing they don't give you is a life vest. They tell you they have them but that is it. Not being close to my family, cramped on the boat, and no life vest was a bit nerve racking. I would recommend not for families and don't bring anything other than yourself.
After all that and a very rough hour+ to get to the swim hole, the water conditions were awful(of course not the crews fault). We were the only boat there. We got in the water for 3 minutes and felt very unsafe with pretty big swells throwing around my 11 year old (and everyone else). I hazard a guess the captain knew it wasn't good before we left but pushed forward anyway. Not sure why this Captain chose to go out but others didn't. It would have made more sense to cancel or postpone. I'm extremely disappointed the Captain didn't call it. My gut was telling me to get off the boat once we found it so crowded and couldn't sit together. I figured they'd not go out if it wasn't worth it. I'm not sure that is true, at least from the perspective of someone who doesn't do it often.
We did see lots of whales swimming around the boat and a dolphin, which was really cool, but at the expense of 5 hours on rough water.
Afterwards, I found out a boat leaves from the Makena side vs the Maalaea Harbor. 3 miles away from Molokini vs 12 miles. I didn't try it, but conceptually that makes way more sense.
All in all, an experience, but I would pick a much bigger boat if I were to do it again and just not go on a rough day. Don't rely on the Captain or crew to make the call based on the possible success of getting into the water. Also, on a side note, I thought the constant tip grubbing was very unprofessional and quite rude. However, this was not the only attraction we did in Maui that practiced tip grubbing. Unfortunate Americans continue this practice of guilting more money out of people. Just charge a reasonable amount to cover liveable wages.