>>56687243I think you might be on to something - I had a search after seeing this post and found out that the manmade walls you often see constructed perpendicular to shorelines are called groynes. The wall our mystery protuberance sits upon definitely looks like it could be a groyne. If we assume that it is, then the object in question is probably a groyne marker, though I'm not seeing any that look like the one in the game. Some are lit, some aren't, but most seem to be taller and thinner. I wonder if Game Freak went somewhere for research and were inspired by a specific groyne they saw?
Lilycove roughly matches up with Kagoya in real-world Japan.