Nautical items are nice. People come to the coast, smell the salt air, and then reach for their wallets. Bell buoys, light buoys, nuns, and cans might sell. There are certainly a lot of different markers out on the water. If they were priced right, sales might be brisk. I would be willing to add a few here and there in my curios.
A thought that comes to mind is the ability to customized a marker. One of my most welcomed sights in my salt water travels is a green can marked "1BI". It marks the end of the North Rip at the northern end of Block Island. It is always a welcome sight, especially in the fog, when you know you've made it through the shipping lanes off Point Judith without encountering the heavy commercial traffic that frequests the area. Leave the markers blank and include a high-quality transparent set of taped numbers and letters. It could be a kind of "build your own bouy" thing. Of course, there are unique markers that shouldn't include such a thing.
Do it! Start with generic markers at $9.99 and see where it goes from there. Sculpt them as they appear on site, in the water. Let's see what happens.
Remember, Harbour Lights listens to their collectors. If you would like to see this happen, put your two cents worth here and support the possibility of this new addition to the HL lines.
Bob