Derbyhaven is a small settlement clustered round the safe anchorage of Derby Haven. (There isn’t a lot to see here – a few houses along the shore and a cafe at the end of the road. Even the chapel is converted into a house.
In the C17th this was a significant port, providing better shelter than Castletown. Now it is used by small pleasure boats and is overlooked by Ronaldsway Airport. This is a good place for plane spotting.
It has a sandy beach which is popular with locals but discovered by few tourists. There is also the start of a lovely “walk”:http://www.visitisleofman.com/things-to-do/derbyhaven-and-langness-nature-walk-p1315501 to St Michael’s Island and round the Langness Peninsula.