Dolphins drown outside of mob activation range.

What I expected to happen was...:
I have an aquarium tank in my survival world and in it I am trying to keep dolphins. I named the them so they wouldn't depawn but sometimes when I leave the immediate area I come back to find one or more dolphins are missing.

What actually happened was...:
After doing research I have found that when you leave the dolphins mob activation range while they are under water they will drown and die. 

Steps to Reproduce:
1. Make it so when you are out of the dolphins activation range it also turns off there ability to suffocate.