Related Clues:

• Old river with changeable current upended bulky swimmer
• Semi-aquatic mammal
• Squid predator
• Huge beast thirty seconds away from island?
• Zoo attraction with a big bite
• Shamu, e.g
• Bicolored ocean predator
• "Free Willy" beast
• Boat in 1-Down
• Two-tone apex predator
• A bird almost taken aback by big creature
• Largest dolphin family member
• Boer War regulars embracing cold killer
• Walrus predator
• Thick-skinned animal, one very quietly entering house