Watching a pair of very large Hippocampus reidi engaging in an extended mating dance while snorkeling over a field of submerged boulders in about 15 feet of water below a cliff in Dominica.
These were the most beautiful seahorses I've ever seen, as well as the largest. Their coloring was subdued but somehow still vivid, with discrete yellow and orange-red streaks on and around the head and dorsal fin. They seemed to almost glow from the energy they radiated.
The pair would twist their tails together while near the bottom and slowly rise toward the surface. As they ascended they would squirm until they faced each other, when the female would deposit her eggs in the males pouch while moving steadily upward. A few orange eggs would miss and trail behind. When they were almost at the surface they would detach themselves from each other, turn and and descend separately all the way to the bottom. They swam amazing fast and powerfully for seahorses as they returned to the sea floor. Once there, they immediately found each other and swam together in a kind of stiff almost formal dance for 4 or 5 minutes, eventually locking tails again and repeating the performance.
During the half hour I stayed with them they did four ascents. I followed them each time. The whole thing was magical, a natural wild purity words cannot explain. I've been a scuba diver and snorkeler for 50 years and have seen many sharks, turtles, huge groupers, even a whale and her calf once. The experience with the seahorses is the one that affected me most.