As a previously land-locked prairie boy, the locks in canals have always mystified me. It's cool to see photos of them in use!

On a semi-unrelated note, everytime you use the word "Shipspotting" in your post I read it as "Ship-posting" and it always tickles me. Shit-posting ships, Ship-posting! It's perfect! (I know you're not a shippy ship-poster, it's just something that tickles my brain)