The reason why he didn't immediately invade was that Dong Tianyu didn't know if there were any ambushes inside, especially after the previous probing, Dong Tianyu wasn't sure if he could still use Sword Control Technique freely inside the Energy Barrier.
A wise man does not stand under a dangerous wall, facing this situation, Dong Tianyu no longer wanted to enter the battleship and slaughter directly, instead, he wanted to first scuttle the battleship and, after it sank to the bottom of the sea, use the Evil Ghosts from the Hundred Ghosts Banner who could freely pass through walls to quickly exterminate all life forms inside the battleship.
After deciding on the third method of probing, Dong Tianyu once again took out several Standard Flying Swords, this time also not carrying any Explosives, and directly attacked the bottom of the battleship from underwater.