The biggest problem confronting Israel in its war on Hamas is how to destroy the Gaza tunnel networks and the terrorist operations therein. Bombing works—mostly—but there’s a better way. Not only would it dramatically reduce Israeli military and Gazan civilian casualties, but it would effectively destroy the tunnel systems for the long term. That solution is to flood the tunnels with seawater from the adjacent Mediterranean.

I worked on the Gaza Strip back in the 1990s. The U.S. government was pouring tens of millions of tax dollars into development assistance there on engineering infrastructure, housing, and related projects. Part of reviewing that work on the ground involved tramping over much of the small territory on foot.

Gaza consists of a strip of beach, back beach, and coastal plain that’s flat to slightly rolling. The territory stretches for about twenty-five miles along the eastern Mediterranean. At its widest, in the south, it’s about seven and a half miles wide; most of it is far narrower, about half of that.

The Gaza tunnel system, mostly constructed over the last forty years, provides Hamas with offensive access to Israel. It also constitutes the terrorist organization’s most formidable defensive redoubt. The tunnels present by far the most difficult logistical problem for Israel in eliminating enemy targets. Open-source maps show at least eleven independent tunnel networks, some nearly adjacent to the sea. The number of independent networks, however, could far exceed that. Hamas claims that the total length of the tunnels is about three hundred miles.