Captured by professional guide and wildlife photographer Hendrik Fehsenfeld, in South Africa's Ngala Private Game Reserve in September, this amazing sequence of photographs show just why these one ton animals should never be crossed.
'This was the first time I had witnessed a hippo fight, so close and personal,' said Fehsenfeld, 40.
'I was giving a tour to some guests on the game viewing vehicle and we were in a sort of stunned disbelief.
'I approached with caution as aggression may divert towards the vehicle .
'When it became clear that these bulls were oblivious to our presence I crept in to get these amazing shots.'
'Looking at the photographs it seems that the bulls are of different ages,' he said.
'This can be seen by examining the condition of the teeth, in particular, the incisors and canines. The challenger appeared to be the younger of the two.'
Fehsenfeld, who has been a guide for seven years, explained that the violent encounter was the result of a territorial battle during the notoriously difficult dry season when water is scarce.
'There are many factors that play into the eruption of a serious fight; the two most common factors being territory and mating rights.
'Dominant hippo bulls do have territories which they will defend. This flight erupted when this younger bull arrived at the water-hole already occupied by the older bull, thus trespassing and ignoring him as the territory holder.
'This is equivalent of a direct challenge.'
For the safety of his group, Fehsenfeld only watched the encounter for a few minutes, but returned the following day to see who had claimed the territory.
'The next morning the old bull was gone. I and tracker Norman found his tracks leaving the water-hole with a blood trail,' he recalled.
'We followed it until the vegetation got very thick - it's not wise to follow an injured animal into thick vegetation.
'So maybe he recovered, maybe he found an unoccupied water-hole. Maybe he lay down in the soothing shade and drifted off. There was no increase in vulture or hyena activity in the area, so perhaps he made it!'