If they made a Shrine for Water Fighting, They be Sirens, Banshees with finand song attracts other then repels their foes, said this already nNow the real question, What happens if some smuck bonesinger builds a Warpgate in a low level area, which gets floated. ? If they open the gate do you flood the warp?
The Eldar don't build warp gates. That's chaos worshiper stuff. We build webway gates. Totally different. And yes, you could probably flood the Webway, but it would take all the water of a dozen worlds. The Webway is vast beyond imagining.