This video from the USA says about itself:
10 March 2016
Whale watchers aboard a catamaran with Captain Dave’s Dolphin and Whale Safari in Dana Point experienced a once in a lifetime thrill when hundreds of common dolphins, without warning or provocation, began porpoising at high speed out of the water. Often referred to as a dolphin stampede, this breathtaking behavior can happen at any time and without any apparent cause. Porpoising is the fastest mode of travel for dolphins because there is less resistance in air than water.
Southern California has the greatest density of dolphins per square mile, [more] than anywhere else on earth. This includes nearly 450,000 common dolphins, the species in this video. Dana Point is one of the best places in the world to see large mega-pods that can number … up to 10,000.