Possible Clues:

• Nautical equilibrium
• Landlubber's lack
• Sailor's asset
• Bearings, of a sort
• What landlubbers lack
• Sailor's bearings
• Sailors should find them, for example, in marine mammals
• Sailor's requirement to listen to view on stages
• Balance on board, say, accepted by catchers of fish
• Give ova protection orally, for resistance to sickness