"It's such a loud sound, when you hear those whales flapping their tails," says Mothes. "We were attracted by the sound."
And, reports CBS News correspondent Mark Phillips, it turns out that one whale was attracted to Mothes' boat -- a bit too attracted.
Sailors on a neighboring boat managed to snap some stunning images of the huge sea mammal shooting out of the water, practically on top of the yacht. The next pictures show the destroyed mast of Mothes' yacht, which the whale snapped like a matchstick as it fell through the air.
"I just saw this huge thing come out of the water, and the mast crashed ... I ducked, I think Paloma ducked," the pleasure boater told CBS News, "the mast missed me by a few inches."
The boat was a mess, but still floating.
Ralph and his wife Paloma quickly checked to make sure their vessel wasn't taking on water, and then they cranked up the engines and left, quickly.
"My first thought was 'let's start the engine and get out of here' -- in case it was attacking us," recalled Ralph.
The Southern Right Whales migrate from the waters around Antarctica to the tip of South Africa every year to breed and feed. Ralph and Paloma just happened to be in the way.
The whale was apparently young, likely frolicking in the deep water and having a good time on its way to look for food.
Sometimes people, and whales, can have too much fun.