I thought there were some underwater plants that they grazed on. I do know they come out of the water to graze at night as well, I was thinking like reeds/grasses that may grow partially submerged in shallow water right along the shore line would be eaten by hippos (in like 2-2.5 ft of water). Do they not? I'm not arguing about hippos with someone whose name is "TheHippoGirl", because I think you probably know way more about hippos than I do! I'm not trying to be stand-offish, I'm genuinely asking because I'm curious.
Also is the aquatic feeder only used as a diving feeder? I've actually never used it in-game somehow and realized I have no clue as to the animation. I was picturing the iconic scene of a moose standing knee deep (for a moose) at the edge of a misty lake with it's head underwater and coming up with a mouthful of aquatic plants. Is that how the feeder works, at like wading depth or is it used while diving? I was kinda thinking the hippo feeding like that, on plants at wading depth; but if they don't realistically do that than of course that shouldn't be in-game.
How exactly are they sitting when just their head is poking out of the water? Are they floating? From my understanding the reason they can't swim is because they're too dense, not crazy so, but like an astronaut on the moon, an astronaut can't flap their arms and fly (a hippo can't kick it's legs and swim), but they can definitely bounce super high and sink slowly. But that would mean hippos shouldn't be able to just float. Or are they kinda standing in shallow water/standing on their hind legs in deeper water (kinda like a crocodilian when they float but with the hippo's back feet touching the bottom)?
I've realized I've actually never seen underwater video from Africa of hippos just hippoing. My guess is it's generally too murky to see much of anything if they tried? And only 2 zoos in the US have hippos, so I haven't really seen one in zoos (I actually have been to Philadelphia Zoo, but it's been many years and I can't remember much about the hippos).
Oh you can argue with me, no problem

I'm not a zoologist and I don't know everything. I called myself TheHippoGirl because it's my favorite animal, that's all. Of course, because it's my favorite animal, I've read quite a bit about them. But yet, I'm not going to pretend I know everything about them. And in fact, even scientists don't. It's a surprising thing but it's a species that has actually not been studied that much compared to many others.
Anyway, they can probably eat a few aquatic plants that grow in border of the water sometimes but like 95% of their diet is grass. During the day, they stay in the water and don't eat. At night, they go out and graze on grass for several hours.
They can't really swim nor float because they are too heavy. So they just use the floor to walk underwater or to bounce back to the surface. When they are in that posture with their head outside the water, their feet are actually touching the floor. That's why they live in shallow water, not very deep water.
And I'm pretty sure there are more than 2 zoos with hippos in the US. Maybe they are less common than in Europe, I don't know, but they are definitely in more than 2 zoos. A quick Google search already tells me they are in San Diego, Cincinnati, San Antonio, Dallas, St Louis, Philadelphia, Busch Gardens Tampa, Memphis...