Judging by the attire of George and Sammy, it looks like a cold Autumn weekend. The old Admiral, who is dressed like a milkman, has no right to shout at passers as he doesn't own the canal, but merely lives on a barge. He seems to be so upset that he's stepped out of the boat, named HMS. I can only assume that he got back in time. Whilst George and Sammy are cramped into one boat plunging downstream with two oars on the same side, a quick way to get nowhere, Lynne and 'Mantha have hired a boat each, and found an area of the canal with no current. It is so calm that they have been able to disrobe in order to pass the old Admiral without any trouble. In fact they have taken their plan a little too far, as the old Admiral now believes he is in love with them. He is not. He is merely lusting after their voluptuous figures. There is no emotional attachment, but it will keep him company over the next few nights.
The lesson here; if you want to pass the old Admiral without him yelling nautical stereotypes, flash your breasts and smile.