how to drown under water

[shade2345]

hi, would anyone know how you could take damage from being underwater too long. i have an item that you could use to breathe underwater but it runs out after 60 seconds. what would the script be if you were to take damage.
im using the skulltag port.

[GreyGhost]

So far as I can see, all you need do is add an airsupply property to your map definition in MAPINFO and give it a value of 60.