Feeding frenzy

Time has passed since anyone's heard from Dr. Catalyst. Emmet and Calvin have even begun to think that the crazed scientist might be gone for good. But then, on a trip to snorkel off the Florida coast, one of their friends is nearly drowned by an underwater monster, with endless rows of razor-sharp teeth. No one is quite sure what they saw. Was it a moray eel? A giant barracuda? There's only one thing Emmet knows for certain. Dr. Catalyst is back...