I was using a Lanturn with Water Absorb. I tried it on anything that I could find that would live a hit. Off the top of my head, there was Skrelp, Clamperl and Frillish on the receiving end, none of which were Confused. I noticed the issue while testing a team Online against a Contrary Lurantis. The same Lanturn had no problem confusing things on Water Surface. I have no mods installed. Yet the problem exists and persists.
The move Whirlpool, when used while the field is Underwater, does not confuse the opponent, despite it being stated in the field notes that it should. It also may or may not get the boost to its Damage Per Turn, though I don't trust myself to notice the difference. It still gets the damage boost all water moves get, just not the side benefit(s?).