Something has gone wrong; the rudder has come off, or the boat-hook has slipped overboard, or his hat has dropped into the water and is floating rapidly down stream. He calls to them to stop, quite gently and politely at first.
Någonting har gått snett; rodret har lossnat, båtshaken har trillat överbord, eller så har han tappat sin hatt i vattnet och den flyter nu snabbt iväg medströms.