I went in April of 2019, and we didn't see any Manta Rays. I understand that there's no guaranteed we'd see them, but I guess my biggest issue was how much down time there was on the boat. We left the dock at 4:30pm, got to the spot around 5pm and then awkwardly sat around and stared at each other for literally 2 hours until it was time to jump in. The captain said we leave so early because he wants to make sure he gets one of the 7 coveted spots to dock to. Since there's so many companies that do this in the same spot, there aren't enough spaces for everyone.
Here's where Manta Adventures could improve: About 20 mins before its time to jump in, another boat pulls up and our captain allows them to dock to Our boat since all the spots are taken. So the people on That tour boat pulled up and were in the water within 20 mins of getting there while we had to wait there for 2 hours?
You should either send a smaller boat out early to save your spot and not have your customers wait on the boat for 2 hours or leave the dock at 6pm and hook onto another boat. I understand you want to be early and 'get a good spot', but everyone was miserable waiting there while watching all the other boats show up much later and not waste 2 hours of their vacation.
If I did this again I would look for another tour that offers a shorter time frame... I believe there were a few I found that were only 2-3 hours total, or go to Sheraton hotel and view mantas swimming for free.