My son(teen) and I did the trip. The trip is amazing.
The wave is not crazy. But I still took the seasickness pill before hand just in case, and it turned out everything is ok. The site is not far from the land from what I can see.
On the way there and back, since it is fully dark, we enjoyed the stary sky.
Now the manta ray is just huge. It is so close that it brushes over my son. But nothing harmful.
We stayed in the water about 30 min. You only need to do a little swimming from the boat to the float where you just hold the bar and put your foot on the pool noodle to relax and water manta rays. We saw 4 of them that night.
A ward of caution: you will get wetsuit (upper body) to protect from the cold walter. But we still fill a bit cold.
Overall, the experience is so unique that it is highly recommended.
Reminder: do not forget the GoPro.