Minke Whale Breaching
Shifter and M&C both suggested Minke Whale for the species of this large mammal. According to wikipedia this whale is around 7m in length, and at least 4000kg. They remain fairly numerous because they are smaller than some of the more sought after whales, and thus avoided being hunted until the populations of the bigger whales had crashed.
The splashes they made were very impressive, but I won't post a picture of a splash. :)
This was the first time I'd ever seen a whale (I'm not counting in captivity or dolphins). I was very happy about our luck of seeing this. There were a number of them, and they were just having a blast jumping all over.