This guy also drops the level 50 RDM JSE leg piece War Hose. I got them last night while camping him trying to get the NIN legs piece. At level 51 he gave me 36 exp, so he's basically EP, plus the extra levels an NM is normally granted to make him more difficult (he was certainly a longer fight than EPs typically are for me).
He only hit me twice, once between shadows castings, but did not interrupt me, and that hit was for 60, and again later with a TP attack that went through my shadows though I didn't lose any. That hit was for 36. Other than that, he never touched me.
I got him by taking the barge from North Landing off of North Sandy at 17:00. When I got dumped at the next Landing, I immediately got back on the barge. When it took off again at a little after 00:00, he had spawned as soon as the area zoned in. He was facing me but didn't aggro me.
Fishing has zero to do with finding this guy. He is purely a normal mob pop on the boat (well, as normal as any NM can be), and since he's undead, he pops at night.