Possible Clues:

• Passively floating sea life
• Despite its weight, the timber will be floating in the water
• Tiny floating organisms
• Board not up to meal of fish
• Mouse, a device that lightens one's work
• Floating organism in the sea
• Seafood? Large amount on board
• Seafood diet and exercise, working to keep thin
• The weight of timber that's been in the water (8)
• Microscopic sea food