Put a timer in the HUD than begins when you submerge yourself in water. The timer counts down to when you begin taking drowning damage (so ~8 seconds). Considering every second you're drowning you take 15 damage, I figure it's good idea to let people know how long they can last without taking damage and come up for air.
This was suggested in another thread not too long ago, but +1 nonetheless. https://www.seriousgmod.com/threads/a-few-suggestions.52790/#post-557015
I don't really have a problem with drowning in TTT, considering most of the maps don't have deep enough water to drown in or any features in the water, but it could be helpful at times. +1
