After reviewing the different options, I decided I wanted to go with a smaller boat that leaves close to the Manta site. Sea Quest gets good reviews and I can see why. This is a great experience, if you are not susceptible to being seasick. We found the crew highly attentive and enjoyable with their light joking and professional approach.
Sea Quest leaves from Keauhou bay which makes it a short trip to the site off of the Sheraton. I had been wanting to do this for several years. I wanted to go with a friend. We chose an evening when the ocean was fairly calm. We both got into our 'shorty' wet suits. Our change of clothes and glasses were stowed on the boat. As we pulled up, I was amazed at the number of lit up 'platforms' with snorkelers floating in the undulating ocean looking at Mantas. Once we stopped, we slid into the ocean off of the side of the 'kodiak' boat (as instructed). It took a while for the Mantas to discover our platform. Meanwhile, the crew was checking with each person insuring that they were comfortable in their masks and the noodle was keeping them angled down towards the Mantas.
I got to see a few Mantas before I experienced my first ever episode of seasickness. I signaled to a crew member that I needed to return to the boat. She helped me over to the boat and onto the deck. She and all the crew were very kind. They offered me ginger ale which helped - for awhile. The crew was prepared for my inevitable reaction to the sea undulation.
I am very sad that I couldn't stay out for the whole time. The crew was attentive to my needs the whole time, including while I stabilized on shore. I'm glad I brought a friend, since I was in no condition to drive. The few Mantas I saw were incredible. I wish I could go again and stay the whole time, but I guess I can't take the ocean movement. Too bad - My mother's family is a long line of seafarers. I guess I got my father's stomach/inner ear.