When mobs are leashed and held under water they break the lead

This is my example:
You're taking a mob under water into an area, it's being leashed and taken under water, the mob is basically at the bottom of the floor / in an area it can drown in, once 65% of it's air bubbles have been lost, it will spin rapidly, and then the rope will break, said mob will quickly swim upwards to the surface, possibly earn Dolphin's Grace so it can get up quicker, and actually survive.

Reason why I think this would be good: How many times have you been leading your pet underwater into a house or something, and you're just about in it, when your pet refuses to go up for air and it drowns? Yeah probably not much, but I still think it would be a very helpful feature.