Endurance and Holding your breath

[DKR01]

So in looking in a lot of places, it makes reference that endurance helps with hold one's breath. I am not sure what specifically it does and if anyone has an answer please can they place where it would be located.

DKR

 

[freyar]

Welcome to ENWorld!

Here's the suffocation rules (from the SRD/DMG):

SUFFOCATION

A character who has no air to breathe can hold her breath for 2 rounds per point of Constitution. After this period of time, the character must make a DC 10 Constitution check in order to continue holding her breath. The save must be repeated each round, with the DC increasing by +1 for each previous success.

When the character fails one of these Constitution checks, she begins to suffocate. In the first round, she falls unconscious (0 hit points). In the following round, she drops to –1 hit points and is dying. In the third round, she suffocates.

There's a bit more about slow suffocation. The Endurance feat grants a +4 to the Con checks required to avoid suffocation.