There are reports about Israel planning to flood Hamas tunnels with seawater.

Here are various posts about this.

Flooding Gaza with seawater in this fashion would absolutely risk ruining the soil and water supply throughout the area. It’s the general equivalent of “salting the earth.”

It is not known if flooding a few select places would have any impact on the Hamas tunnel system. Such a move would only bring more international condemnation and no guarantee of having any meaningful military impact.

The whole plan is really quite crazy and insane. The fact that they are considering this is just more proof that their ground forces have failed to achieve any meaningful military gains against Hamas thus far.