Tanks a sub explosion while weak

Then Captain Sterenko and the rest of the crew heard it-- the terrible roar of an incredibly gigantic beast of prey.
Suddenly, the damaged hull of the Akula split in half.  Millions of gallons of ocean water rushed into the superheated reactor core and instantly turned to steam.
The resulting explosion was horrible.  The super-heated steam ripped the submarine to piece.  Chunks of the vessel and its contents were scattered along the ocean floor for miles.  A huge steam bubble erupted on the ocean’s surface.
Even though the core of the submarine’s reactor stayed intact through the explosion, radioactive material leaked from it and spilled into the water as it slowly sank.
Nearby, the mysterious creature that had destroyed the submarine fed on that radiation.
It fed and grew stronger.