Possible Clues:

• Tank seen in part of ship next to Channel Islands
• Is the bird underneath the cold water tank?
• See is the bird the one with the water in it
• Tank - sac of body fluid
• Water container
• Not a brothern, perhaps, by the sound of it. Does that hold water?
• Cretin's let loose in tank
• Storage tank
• Well
• As water container, nicest possible rain trap