Growing up in the Midwest, you sort of get used to severe weather like tornadoes. People down on the coasts probably get used to waterspouts. Simply put, a waterspout is a small tornado that forms over water. They're fairly common, but can still be very dangerous.
A lot of the time, they stay out over the water, but sometimes, they can move over land and become a tornado. That's what happened here.
This waterspout heads over land, destroys some buildings, moves back over water, and then back on land, just tearing things up as it goes along.
The guy who filmed this was out on his deck, about to start some grilling, and ended up being SCARY close to this waterspout.