I was able to get a paywall busted version of the WSJ report. archive .is doesn't always work on them. https://archive.is/n2JCW
A spokesperson for the Israeli defense minister declined to comment, saying the tunnel operations are classified.
Flooding the tunnels began around the time Israel added two more pumps to the five pumps installed last month & conducted some initial tests.
Some Biden administration officials have been concerned that using seawater might not be effective & could endanger Gaza’s freshwater supply. Egypt in 2015 used seawater to flood tunnels operated by smugglers under the Rafah border crossing, prompting complaints from nearby farmers about damaged crops.