I think now it is time for some liquids. For this I've built a little basin in our copied room of the last tutorial.
Create a new brush, a bit lower than the basin and use the texture liquids/clear_ripple1.
Repeat this for the brush in the corner:
If you compile your map and play it ingame, it already looks like water but there is an unattractive dark line.
For fixing this bug select one of the two water brushes and press h. Don't worry. It isn't deleted. It is just hided. If you press shift+h it should be there again. So hide the brush again and press Esc for a precaution. Now select the visible face of the other waterbrush (shift+Ctrl), go to the textures list and select common. After that open the texture window (t) and click on "nodraw":
Press shift+h to unhide the brush and hide the other one. Repeat the nodraw step for the other face:
The line shouldn't occure ingame now, but there will be a nice flow between both water brushes instead. You should always do this with liquid faces which are lying directly to each other. Also for lava brushes. If you want to have lava instead of water just select a lava texture out of the liquids list. Normally the lava should already hurt your player when you are getting in contact with it. The same with slime.
Here you can get the maps for this tutorial (place it into baseq3/maps):