A Gauge is like a time that tells you when to get up. So if you've run out of gas they the gauge will tell you
Keeping the air inside of the tank to breath the air out of it
You use snorkels to look and see underwater.
You use a diving suit to swim underwater and so you won’t get scraped on rocks and hurt your skin.
you use a life jacket to keep you safe and make you float if you’re lost in the sea.
you use a diving gun to kill the food you want to eat.