Baryonyx are quick like Allosaurus and do just as much damage (but don't get a pack bonus). They don't use oxygen for swimming and can sprint in the water. Right click in the water does an AoE stun that lasts about 10 sec. Their 'C' is a... Taunt? They also jump and you can fire a weapon from their back.
It's like a small Allo combined with a Kapro, in my opinion. Useful on both land & in the water. Use its secondary attack while swimming to stun, attack, and harvest. Does NOT stun Cnidarias, though, so do not expect to overpower them.
Great mount for the swamp. Riding in 1st person is just below the tree line. It's tall enough to avoid some kaprosuchus leaps. It has a high torpor to survive the snakes/frogs. Eating raw fish helps it heal super fast. It has a good sprint speed, can jump and can swim. My new favorite mount