Well, they do. A lot.
The following clip shows how, around the islands of Hawaii, dolphins and humpback whales have been engaging in some form of sea wrestling, with the whales lifting the dolphins out of the water and letting them slide down their backs.
There are a number of pictures across a number of locations, meaning that this behaviour is more widespread than first thought.
The observers noted that the behaviour was unlike other animal symbiotic relationships in that it was not for a beneficial purpose (such as parasitism), but almost certainly for play.
Scientists who investigated the phenomenon noted that there is also zero evidence that the behaviour was hostile – but a quick look at the clip will show you that.
Like me, you are probably upset that whales and dolphins have been hanging out together all this time and they didn’t tell us about it.
We are unsure exactly what the whale gets out of this situation, other than perhaps a nice back rub, but the pictures certainly make me want to put on the ol’ dolphin costume and head down to the beach.