Yes PA pls do it

+1 

I agree with OP, this idea is solid. 

100% agree. There's ZERO reasons why a T10 Dine needs a water stamina bar. It's not competing against boats or anything alike, it's not like you can barter with it, you can't use charge on water to hit anything, there's absolutely no reason to limit its water running for any reason. 
It will not make it Overpowered, it will just make it comfortable to use so you don't need to pause mid-running on an island, stand still for 10 sec each time,  just to fill up a useless stamina bar.

Totally agree. It'll be more chill and fun rather than ingame exploits. Or at the very least, have enough stamina to go from Lema Island to Oquilla's Eye comfortably. Although the pause in the middle of random island to regain stamina can be annoying. Definitely not OP suggestions if compared to doom/pega.

Yeah, Mythical Dine should definitely have the limitation removed for running on water. Letting it run in Margoria should be fine too.

True and mega real

It definetly needs to be removed. Those are unique horses. You should run on water without stamine... Also i would like for the pegasus to be the same. Just to be able to fly , glide and flout without any restrictions. 

Nah no thanks, thats a step too far letting him go into ocean.

I agree the stamina bar should be removed! And curious the reasoning to even have it for the current game. I can't think of anything that could be exploited, even out in Margoria. You need a boat to barter/sea monster hunt. Traveling by sea to the land of morning light is pointless with fast travel now.