stern light
This is a link to an article for building yr own, I thought it was pretty good. I use a headlamp and carry a big ol' 3 cell maglight just in case. If you paint yr paddle blades a bright color and shine yr headlamp on one yr pretty visible. Any type of strobe will make you a lot more interesting to the USCG and/or Harbor Police, strobe's are generally considered emergency signals. It's a good idea to have one, however, if you do have an emergency. USCG will only require a flashlight to warn oncoming boats and you should have a horn.
And speaking of Joppa- Shaun, thanks for the suggestion to go there. I did, it was a great yak spot and lot's of fish. Not particularly cooperative fish, but they were there and I had a great day. thx