[Eleutheria5]

Incredibly, yes.

Flooding Hamas tunnels with seawater risks ‘ruining basic life in Gaza’, says expert

https://www.theguardian.com/world/2023/dec/23/israel-flooding-hamas-tunnels-seawater-risks-ruining-basic-life-gaza-expert

(incidentally, salt water would be a bad idea. Flood the tunnels with fast-setting concrete instead.)

[rktman]

Or spray on foam insulation. Might be able to do it with a remote vehicle.