This is the scary moment a charging hippo bit down hard on a boat's rear motor with its massive jaws.

Jackie Boshoff was on a river tour down the Chobe River, Namibia, on March 22 when the group came across a group of hippos bathing in the water.

Dramatic footage shows the moment a large male suddenly charged at their boat causing the skipper to try and escape.

Unfortunately the boat ran aground leaving it at the mercy of the huge hippo who then chomped down on the outboard motor leaving the plastic surroundings cracked.

Jackie, 55, said: "I actually couldn't believe what was happening in front of me. You hear and read about this stuff, never thinking it could happen to you.

"Everyone on board the boat actually remained very calm, including me. Fortunately nobody panicked.

"We approached the pod of hippos, like our skipper always does, and has done for over 13 years in this channel. The pod is known to sometimes be aggressive, like hippos tend to be.

"Our skipper is always on alert for that kind of behaviour. We were quiet on the boat, not making a lot of noise, and the engine was off as we approached them from a safe distance.

"Then suddenly one particular male hippo begun chasing the boat out of nowhere.

"When our skipper realised there was a potential problem of him hitting the boat, he turned the boat and headed away.

"But because he was watching the hippo and not the front of the boat, we went into shallow water and the propellor got stuck in the mud.

"Only later when we reviewed the footage could we see what appeared to be a small calf following the male hippo as it charged us.

"It could be a very young calf and he was just super protective of his young."