It depends on which part of the environment the heat is being exchanged with - if your watercooling system is releasing heat to the ground under your house or a somebody else suggested (which is even more effective) a river next to your house, it’s not at all equivalent to air cooling?

Further, the heat storage capacity of a material depends on both the kind of material and its mass, so almost all liquids have a higher heat sforage capacity per unit of volume than air (certainly water does) and solids even more (much more, given their much higher mass) so even in the big scheme of things (i.e. were will most of that heat end up in given enough time), even heat released by a watercoolong system to the air will mostly end up in tne Earth’s crust and oceans and only a tiny fraction of it will remain in the athmosphere.