Funny thing is the males are very territorial. If you see a group like that it's most likely one male and the rest are female.. And all the kids you see there are female.
Hippos can't stand another male being around. I got on a boat with my girl and we went out looking for hippos with a guide. We found one solitary one first..and a little kid. Guide said it's her son and they hide them aside from the father and sneak out to go feed it

Cause pops will kill it if it's around. Then some 200 meters away we found a big group with one male that sped towards us. I still have the video in my cellphone. We watched them for a while then they disappeared into the tall grass.
What I learnt is they stay in water all day to keep cool. Then wait for evening to arrive and they go out and graze at night. Eating tons of grass. And then they can't topple your boat unless you are in shallow water and they have footing on the ground. Also they can't cross ditches. They'd eat a ton of food from people's farms and the trick was to make a ditch all around