User blog comment:RG4215/Ocean Masters Demise/@comment-4803246-20120520230339

I don't think it really matters what happened to Ocean Master; the sole reason he was done away with in season two is because he didn't get a single line in season one beyond Prince Orm and that one time behind the light-screen. I think Weisman and Vietti were planning to give him his own episode or two at some point in season one, but then it just didn't work out. They just never had the time and/or the finances to give him a speaking line. Because of this, they essentially bailed on his character in Invasion and replaced him with Black Manta, who has much more of a presence in YJ. I suspect that the official in-story reason is because he was unmasked, probably around the same time as Tula's death.