I’ve been thinking about the flooding for a while and thought about what the savages would do to the hostages. One alternative is to leave them down there to drown and then blame Israel for killing the hostages. I know the hostages are very valuable to Hamas as leverage. I also know that it would be hard for them to blame Israel because the only reason the hostages would drown was if Hamas prevented them from leaving the tunnels.
You have to assume ALL of the hostages are already dead and move forward on that assumption.
Flooding the tunnels seems like the least expensive, in terms of IDF casualties and financial cost. as well as being possibly the most simple and effective solutions.
It is unlikely that Hamas has these tunnels set up like a sub with water tight doors and separate air handling capabilities.
Likely that the tunnels are mostly all connected and the highest value positions are the deepest.