Making an oxygen system

Hello,
So I was playing some games and wondered how they did the oxygen system and how they decide if the player is underwater or not. Do they use triggers? I was thinking they would attach an object at the position of the mouth/nose of the player and would check if that object collides with the triggers or something like that. I might try to make it in Unity.. Any ideas, or clues of what the best system would be? Thanks.

 

Anyone could send in the right track regarding an oxygen system with underwater/surface detection?

 

There are a handful of ways to do that. But you can use triggers/sensors, with some scripting for that. That is one way to do it.

In some older games, the devs would sometimes put the trigger, on/over the objects entire body, like for example a human or a doggy. If the trigger is on/over the body of the human or doggy, and is completely underwater, or hits a certain point underwater, the oxygen system or meter starts.

Another method, is to use a raycast to detect if the character is in the water, or not, but I haven't used raycast much, so I am not a big expert on it.