Using a water storage tank as an ambush was indeed a good idea.
Although Bai Fan could sense nearby water and discern enemy positions, if the enemy submerged themselves in the water, he would have difficulty sensing them.
Wu probably also took human psychology into account, guessing that Wang Ran and the others would let their guard down after clearing out the enemies at the elevator entrance. This would be the prime time for an Amalgam Monster to rush out and achieve the easiest victory.
Regrettably, Wang Ran had control over the future within ten minutes.
To obstruct him, one needed an absolute power to shatter those ten minutes, but the Doomsday Apostle clearly did not prepare such a strategy against him.
"Let's continue downwards," Wang Ran said calmly, "Everyone, stand close together. I'll withdraw the mud and magma beneath our feet and move vertically downwards from here."
Yiya silently wrapped her arms tighter around Wang Ran's arm.