In the current Arma 3 build units are not able to heal themselves when they stand or crouch on a shallow water surface - I assume the first aid action is displayed only when unit can go prone, and this makes the game severely less playable in swamp areas or maps like Tria. Since the healing action and its effects are the same no matter what stance a unit has, I suggest adjusting the action condition so it allows applying first aid on Z axis that allows crouching, but not being prone.