Hmm... A few simple way to do it would be to make it so it's limited and you can only use it for a short time before needing to recharge (though it will be a quick recharge). Another would be to make enemies or only certain enemies be invisible when you use it so the player would need to deactivate the water vision in order to see incoming dangers. You can also try restricting the player's movement so they move slower when using it.