Former Belgian fishing vessel POSEIDON (Z.580), withdrawn from fishing in 1999. Looks from skylight and gunwales as if some work now being done. Compare 2009 photos at http://www.scheepvaartwest.be/CMS/index.php/fishing-boats/3110-z-580-poseidon
and when new:
http://www.vliz.be/cijfers_beleid/zeevisserij/photo_gallery.php?album=953&pic=60208

POSEIDON
61gt, 20.64m
built 1963 NV Scheepswerven De Graeve, Zeebrugge

Last owner found: Ronny Blomme, Zeebrugge. Was intended acquisition for by Sea cadets in 2014 for inland use: https://www.nieuwsblad.be/cnt/dmf20140124_00946094