HMS Nautilus is on patrol off the west coast of Africa, intercepting the American slave ships that were trying to purchase cargoes of slaves and then take them across the Atlantic in loathsome conditions. Slavery had been abolished in British territories in 1772, many years before, and the British were actively policing African waters in the hope of deterring the Americans and the Portuguese from retaining the slave trade.
"No, sir; ashore."
"I tell you it was at sea, and it is the craft we are after. Now, my lads, give way."
"Why, we're among the trees again."
"Yes, sir; shore's this way," said the coxswain.
"Then where in the name of wonder is the sea?" said the lieutenant, in an angry whisper, as the tide bore them along, with the men's oars rattling among the mangrove stems.
"I think we've got into a side channel," said Mark.
"Rubbish! How could we?"
"Beg pardon, Mr Russell, sir," came from the boat astern; "we've got into a sort of canal place with the tide running like a mill stream. Hadn't we better lie to till daybreak?"
"Better sink ourselves," growled the lieutenant. "Here are we regularly caught in a maze, and that schooner getting comfortably away to sea."
"'Fraid so, sir," said the boatswain. "That there was a light showed ashore to warn 'em that we were in the river; some of 'em must have heard."