A seal in Øresund

There are a number of seals in Øresund, although I have not yet managed to see one. Or actually I have seen one, although I was hitherto not aware of it! Today, when looking at some of my evening photos from February 21, I noticed that there is a seal resting on a stone in the water!

The seal appears to have some kind of light marking installed on it - maybe to make it easier for ships to identify it?