For SE hope one spawns near the beginning of the blue cave getting one out is really hard and most likely have to be done during the night since if heir sleep meter is too high they will drown because they won't swim to the surface.
What you want to do is set it to stay awake in the day it will build up torpor and get knocked whiles it's knocked out it will eat much less food as a baby but after it wakes up from torpor you have to set it back to stay awake
Best place to tame is in Central cave (next to volcano). Drag it to the water and it will get torpored by itself due to being unable to sleep underwater and the good thing is that oxigen won't go down. Wait for it to starve an you'll have a fairly easy tame.