Possible Clues:

• Heavy breather coming round to eat spread
• Another name for the orca
• Common name for killer whale
• Pugs romping round animal: huge creature
• Dolphin’s mostly well out around slipway perhaps
• Whale beginning to swim up, something oily coming to surface
• Sea creature — lightweight animal lacking tail?
• Lightweight Manx cat's a killer at sea
• Killer whale's cousin
• Heavy breather's racket disturbing theatre cat