We stayed for the winter, in part, to see the whales in Hawaii in the winter months. We saw them starting yesterday, during a boat ride with Megan’s family and friends at sunset. We saw them spouting as they come to the surface to breathe, breaching – when they jump out of the water, and flipping their tales as the dive. But today, we sailed to Molokini, a small cater south of Maui, and spent eight hours on the water, and saw much more whale activities, up close and personal. In particular, one the way back to Lahina, at sunset, we heard and then saw, rather close to the boat, a whale thumping his tail repeatedly, for some unknown reason. Megan caught a video. Take a look. More to come…
avionbianca 
Very cool, and also concerning … Was that from some sort of distress?! I am counting on you two for some research ( locals who have seen before?!)! And I am looking forward to more videos! :- )
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HI Nancy: A quick search on the internet suggests whale tail slapping is not well understood, but could be some from of fishing known as lobtailing, that is learned by males when around 2 years old. The sound stuns fish, making them easier to catch. The behavior is also possibly aggressive (in pairs), or establishing territory (by single whales). Whales come here to mate and give birth, so I bet it is a mating behavior. I will ask around to learn more.