Most efficient way to check player water level?

I was planning on putting an entity:waterlevel check to determine if a the player should be damaged in the think hook of a weapon, but I feel like this would be grossly inefficient.

The check will only need to affect a player assigned to a team, and the player only has access to one weapon.

I am modifying the SCP Breach gamemode to accomplish this.

WaterLevel is already determined in the engine’s movement hierarchy for players, and the player function is just an accessor to that pre-calculated value, so there’s no efficiency concern in using it.