This tutorial shows how to make swimmable water in Vavoom Hexen. I’m going to start from the top and remake the test level I made for learning how to make water and I’ve written this presuming you know how to use WadAuthor. If you don’t, use the WadAuthor tutorial in the help file.
Firstly make a polygon with 4 sides and a radius of ‘800’ then inside that sector put another 4 sided polygon but this time with a radius of ‘400’. This new sector will be our pool so we need to make it deeper so change its floor height to ‘–200’ and while you have our pools properties up change the sector tag to ‘1’ then click ‘OK’.
Next build a rectangular sector like I have below and bring up the sector properties and change the floor and ceiling heights to ‘-16’ and their textures to ‘X_005’ then change the lighting to ‘255’. Afterwards, close the properties box.

Now the hardish bit, Bring up the properties of 1 of the sidedefs of our third sector and select ‘Special>3D floor( tag)’ and change the argument that is available to ‘1’ then click ‘OK’. Now pick a different sidedef from our third sector and select Special>Contents( type, trans, flags)’ then click ‘OK’. Finally put in a player start then save and play your level.
Ok that’s about it. You can change the values of the ‘Special>Contents(type, trans, flags)’ and see if anything happens. If you’d like to make the water darker, you can do this by changing the brightness of the third sector.