When "fire in engineroom lower level" was announced, due to water in the main lube oil pump motors, a man in the aft end of engineroom upper level opened the watertight door into the stern room, which swung into the stern room, to retrieve a fire extinguisher. Just then the up-angle increased dramatically and the bilge water began pouring in. The door was shut before the boat surfaced. With the boat on an even keel, the water came up to the deadlight in the door.