Welp. I did some research on how the Elemental Plane of Water was supposed to work in AD&D and among other things the Elemental Plane is supposed to have low gravity and zero water pressure. So... Melee attacks on the Elemental Plane of Water are always at Disadvantage unless the combatants are grappling or unless the weapon being wielded is a dagger, firearm, javelin, spear, or trident. A ranged weapon attack automatically misses a target beyond the weapon’s normal range. Even against a target within normal range, the attack roll has disadvantage unless the weapon is a crossbow, a net, or a weapon that is thrown like a javelin (including a spear, trident, or dart). Creatures without a fly speed have their base speed reduced by 10 feet. Those with a swim speed double it. Everyone can make an Athletics check to increase their speed by the result of the check, DC 5, if they fail they go into a spin and can't move this round (or at the DMs discretion might move in a random direction). However they can only move in straight lines. Once they begin to move can only change direction by pushing off another object, and the speed of their drift is reduced by 5 feet or 10 feet each round depending on if they are moving through air or water. Creatures encumbrance limits increases ten fold, essentially they can carry 100 lbs per point of Strength. Spells cannot create fire in the Elemental Plane of Water. Some spells have altered effects for instance the Lightning Bolt spell creatures a burst centered on the caster with a 25 foot radius that deals 8d6 lightning damage, or half that on a successful Constitution save. The Destroy Water spell deals 1d10 necrotic damage to water elementals that fail a Constitution save, while Create Water will restore 1d6 hp to water elementals.