I was recently on a server with these things that looked like portals except with water, it was before the aether mod. I was wondering, how do you build them?
I don't want the Aether or Portal mods.
The old ServerPort plugin, which allowed traveling beetween servers, had one of these. Sadly, the author has abandoned the Bukkit version of his plugin, and there are only Nether Gates now. http://forums.bukkit.org/threads/inactive-tp-server-port-v377-teleport-between-servers-1000.777/
You can see the portal here, to check if it's the one you meant:
It is only a skin pack, you can edit it yourself or download them online
In vanilla Minecraft, creating this effect is simple. First, make your portal. (Do this any way you would like.) Next, put pressure plates in front of it. Lastly, put command blocks under the pressure plates with a command such as
/tp @p ~ ~ ~.
Your problem is that you can't make water portals in vanilla minecraft. If you want to, though, you can always get a bukkit server and get the water portal plugin.