The V-shaped rock formation below, discovered off the British coast, was constructed to trap fish as the tide flowed out. This is ingenious and possibly more effective than any fishing method we use today. And no fuel is burned with a boat. (We spend nearly $100,000 a year on diesel fuel fishing on my boat.)
Google-Earth-reveals-fish-trap-rocks-1-000-years-ago-British-coast.html?ITO=1490
