This video clip brought back many happy memories. It was taken in what is today the iSimangaliso Wetland Park, but when I visited it was known as the St. Lucia wetlands. Bull sharks (often referred to as Zambezi sharks in Southern Africa, partly due to their habit of swimming for long distances up that river) can exist for extended periods in brackish or even fresh water, so they're often found in the river estuaries of the wetland park.
Hippos attract lots of smaller fish due to their habit of defecating in the water, using their tails to spread the dung along the river or estuary bottom. The fish feed on the waste. The shark was obviously after those fish (it's far too small to take a hippo, even a young one), but in trying to get at the fish, it began to bump into the hippo. This is not recommended for any species whatsoever, because hippo are more than a little paranoid about being bumped by things they can't see in the murky water.
The shark was lucky to get away unscathed. Sometimes they don't.