"They are friendly because they are all grass-eaters. The buffalos cannot even fight a hippo; the hippo also cannot fight a buffalo, because they are all grass-eaters. You know it is better to fight a predator than fight your fellow friends," Peter said.
However, they have been known to tangle with predators like lions or crocodiles on occasion.
Hippos are a key part of an ecosystem that includes a variety of creatures, from goose-stepping cormorants to regal eagles to dancing antelopes.
On our visit to Uganda, we also encountered an aggressive male water buck.
These animals might seem mellow, but they aren't afraid to use their huge, intimidating horns to attack. Our guide and his colleague throw rocks to get him to move, but he wouldn't budge. We had no choice but to opt for an alternate route.
While wildlife in Uganda is thriving, right across this lake from where the hippos and their animal friends are living in relative peace is the Democratic Republic of Congo, where an all-out civil war has resulted in the massacre of not only people, but also hippos.
"Their numbers have reduced dramatically over the last 35 or so years. We've seen a reduction of 95 percent," said Kimunga Mugo, who works with the World Wildlife Fund. "It's basically a slaughter. It's a massive slaughter."
There were 30,000 hippos in Congo in 1974. Now, there are only 800.
They're disappearing because they're being eaten by competing bands of marauding militias.
"The armies are living off of hippo meat, because basically when they're out in the bush, they don't have any other source of food. They have to get their protein, their meat, from somewhere. They're basically decimating the population," Mugo explained.
Civilians are also eating the hippos, an appetite fueled by desperation and also by an ancient belief that eating hippo meat will make women fertile and provide more children.
The slaughter of the hippos isn't just bad for the animals themselves, it has also had a devastating impact on the environment, creating a vicious cycle of starvation. Hippo dung is a food source for the fish in this lake. As the hippos disappear, so do the fish, a major source of food for people around here.
Conservation groups like the World Wildlife Fund have been working feverishly to stop the killing of Congo's hippos, but it may be too late. They have helped move refugees out of national parks and out of the hippos' habitat.
But at least in Uganda, there are so many hippos that we literally bumped into one with our boat. Wildlife officials view the healthy population here with mixed feelings. There is a sneaking suspicion that the only reason there are so many here is because they are running away from the carnage in Congo.