The regen system is very strange and to be honest I don't really know exactly how it works.
Basically pets were set up with like:
0
1
2
4
But obviously it regens more than 0 for the low level pets
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So basically what I did was change all of the water pets:
0 -> 1
1 -> 2
2 -> 4
I think this should double the regen rate, but I may have to look into it in more detail with regards to exactly how much HP regen each of those equals.