VIDEOS:
The Drowning Music
You get 30 seconds in the water in most 2D Sonic games (and some 3D ones such as the Sonic Adventure series). For approximately the last 10 seconds, the infamous drowning theme plays, warning you to get out of the water or find an air bubble.
Example of:
Critical Annoyance
Green Hill Zone
Example of:
Green Hill Zone
Egg Mobile-H
Example of:
Warm-Up Boss
Marble Zone
Example of:
Lethal Lava Land