potting in water is do-able however it is hard because throwing a pot in water is like shooting an arrow in the water, very slow. So items like gapples is needed within the gamemode to increase survival rate or else players can just win purely through numbers.
If u say it is easy to win a 1v2+ through gapple pvp, that is actually really hard as pots are limited in the inv. The opponents can just go in taking turns wasting their pots and eventually that solo player would lose by running out of healing