>>44746548All surfable pokemon rides can also dive but only if you have the scuba gear key item. This item prevents you from drowning and adds some minor realism.
Pokemon that aren't water type must be switched out every 5 turns, if they can't they will automatically faint. Why only water types and not all aquatic pokemon or ghost type? Well, why can't all flying types learn Fly? OP wanted a shit gimmick.
At the start of underwater battles the text will notify you that you are submerged in deep water. Furthermore water moves will have an attack boost. Electric attacks target all adjacent allies and opponents but does reduced damage. All fire type moves will fail. Steel and Rock will have reduced priority by -1 but take reduced damage from water type attacks. Poison type attacks does reduced damage but also targets adjacent opponents including the attacks chance of afflicting poison status. Pokemon with abilities that are effected by rain will have their effects activated. Gravity based attacks will do reduced damage. Some ground based attacks like earthquake will also fail or alternatively do reduced damage.
These battle conditions can not be nullified unless an effect is strictly specified to alter a submerged environment or to give a unique expemtion to a pokemon.
Fairy types that are sent out will instantly drown and be removed from the players party, blub blub. 
