Possible Clues:

• Marine creature in hold at sea retains power
• Clever swimmer working on DPhil
• No DPhil organised for fungi
• Sea-creature in hold moving around quietly
• No go for Arabian thoroughbred or marine mammal
• Intelligent sea creature
• Mahimahi
• Creature in hold knocked out, keeping quiet
• Crime boss admits Little Philip Cook presumably sleeps with the fishes
• Hard Rock Stadium gridder