Getting up close and personal with whales is on most people's bucket lists. But these kayakers probably got a little closer than they were expecting at Moss Landing in California over the weekend. The footage was released by whale-watching company Sanctuary Cruises, and shows a beautiful whale launching itself out of the water before landing almost directly on top of a kayak, knocking the passengers into the water. You can clearly hear a concerned onlooker asking "The kayak! Where's the kayak?!"

Luckily, the kayakers resurface a few second later and were seemingly unharmed. Even though the angle that passenger Larry Plants filmed this from makes it look like the humpback landed right on top of them, it was a near miss. Which is lucky, because humpback whales can weight up to 50 tonnes, and if they'd been hit they would have been crushed to death.

It's for this reason that current guidelines don't recommend people get any closer than 100 m to whales, or 300 m if they're in a boat. But it can be hard to know exactly when a whale is going to pop up under you when you're on the water.

What's interesting is that scientists still don't really understand why whales jump out of the water like this. Some researchers think that breaching is a competitive display between males.

"Others suggest it may be a warning for perceived threats, such as predators, or even unwanted attention from vessels," whale expert Chandra Salgado Kent from Curtin University in Australia told Australian Geographic back in 2013.

Another possibility is that breaching may be a form of long-distance communication, allowing whales to cause sound waves that can travel quickly in water. It might even help them to stun their prey. But most scientists now agree that there's not one reason for the breaching behaviour, and it serves a range of functions.

Watch the video above to see the behaviour in action, and just hope that you never get unlucky enough to see one that close up. And everyone going whale watching this migration season, remember to keep your distance - they're giant wild animals, after all.