Northern Light
Superstar
From Amusement Insiders (yes, the same YouTuber famous for filming Yukon Striker's construction in Canada's Wonderland using a drone):
There's speculation that 100 Kellogg's Lane (which owns an indoor entertainment complex at that address in London, ON) purchased Marineland. The video contains an error (he said Hamilton when 100 Kellogg's Lane is actually in the eastern part of downtown London).
Definitely one of the groups to have kicked the tires on this site.
To my understanding * not first hand knowledge; and also reported by A.I. ....... Hershey Park (as in the amusement park) also came by for a look-see.
I haven't heard of anyone else in the amusement field, having had a close look, but that doesn't mean it hasn't happened. There's no way Cedar Fair (owner of Canada's Wonderland) isn't aware this site is in play), I would assume the same of Six Flags, but as both have parks nearby (Wonderland and Darien Lake) they seem unlikely bidders.
I had heard rumours of the folks from Dollywood thinking about things here, but have been unable to obtain corroboration on that.
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As to whether a sale has actually gone through at this point, enough UT members have access to the relevant info to let that be known should they choose.