Related Clues:

• Ringlike formation
• Bikini, notably
• Site of a shipwreck, perhaps
• It's often formed around a sinking tropical island
• Castaway's locale, maybe
• South Seas spot
• Key chain?
• One in a chain, often
• Lagoon creator
• Ringlike island
• Bikini, among others
• It consists of a circular coral reef surrounding a lagoon
• It might be just below the surface
• Isle with a lagoon
• Atomic test site, perhaps