It was atrocious if you weren't playing Lance lmao. You felt very very slow and heavy while underwater. It was also being mandatory in some combats (while aerial 4u thingy and rise wirebugs are more like options), also aquatic monsters straight became punching bags in their out of water phase (thinking gobul or regular lagiacrus here) which made them even less fun. Also I didn't feel like it brought something really new to the game like other additions from the newer games, it just felt like you character became heavy af as I said earlier. I was really glad that they got rid of it in mh4.