Possible Clues:

• Undulating furniture
• Spot for a swell sleep?
• Sloshy sleeper
• Whether to start chopping up bad tree? Sleep on it
• Wife-beater perhaps the first to drown here?
• Place to sleep that may leak
• In drought, gardener may sleep on it perhaps
• Heatable mattress
• It may rock you to sleep
• Undulating mattress