Seawater.

This is coolbert:

Not merely being considered. At this point is the reality, the tunnels of Gaza being flooded with seawater by the Israeli defense forces. An event apocalyptic in nature.

 

"Israel Weighs Plan to Flood Gaza Tunnels With Seawater"

"Move could drive out Hamas fighters but threatens to foul Gaza’s freshwater supply and damage infrastructure"

From https://www.wsj.com | Nancy A. Youssef  | Warren P. Strobel  |  Gordon Lubold | Dec. 4, 2023.

"WASHINGTON—Israel has assembled a system of large pumps it could use to flood Hamas’s vast network of tunnels under the Gaza Strip with seawater, a tactic that could destroy the tunnels and drive the fighters from their underground refuge but also threaten Gaza’s water supply, U.S. officials said."

From my perspective, the greatest danger will be to infrastructure above the tunnels that will become flooded. Will cause the ground to subside with the foundations of the buildings becoming unstable. You might have these large buildings made of cinder block collapse in the entirety. 

coolbert.