Possible Clues:

• Balance on board, say, accepted by catchers of fish
• Give ova protection orally, for resistance to sickness
• Sailor’s stability
• Balance on board
• Swell accommodation!
• Sailor's requirement to listen to view on stages
• But they won't help you walk on water!
• Ability to maintain one's balance on a ship
• Sailor's requirement for supports under the ocean?
• Resistance to seasickness, say, among swimmers