Pacas (Cuniculus paca) are a yard long and weigh 20-30 pounds. So basically split the difference between a guinea pig and a capybara, and you’ve got a paca.

Who is, incidentally, above this shit, sir.
Much like the capybara, they’re excellent swimmers and will go for water when threatened. They can actually stay submerged for a full fifteen minutes, which is very impressive for a terrestrial rodent. They prefer forest environments to open territory, though, since they’re not exactly built for distance running with those stubby little legs of theirs.
Since pretty much every cat on the continent tries to eat them, they live in burrows they dig and then camouflage with brush. And I’m not really exaggerating, there. Pretty much literally every cat on the continent, even the ones that aren’t any bigger than housecats, try to eat these guys. It’s to the point where their babies are actually rocking scale mail and the mothers dig nursery burrows that even mom can’t fit in. She has to call the baby out to nurse and run around.
Pacas are surprisingly vocal for their size. They’ve basically got drums instead of expanding pouches in their cheeks (suck on that, hamsters), and they can make a sort of growling, grunty noise that’s a) really loud and b) used to communicate with other pacas. They’re not really terribly social, but the babies stick with their mothers until they’re about a year old, which is some next-level parental effort for most rodents, especially for rodents whose babies are born fully-furred and mobile.
Females can give birth multiple times per year under favorable conditions, so you can get sort of roving bands of steadily miniaturizing pacas all getting into fruit and gnawing buds off understory shrubs. If you needed more evidence that these little bastards are completely ridiculous, they bang in the water, and females communicate receptiveness to the male’s advances by jumping up and down in place.