Possible Clues:

• Cheer up
• Gull's counterpart, in a maritime pun
• Number three in aquarium feeding young male dolphin
• Marker bobbing on the water
• Warning floater
• Marker for boaters
• Ocean marker
• Something often seen heaving on 'Baywatch'
• Distinctively-shaped coloured float
• Sounds as if in the lad there's nothing to purchase