Yes it was (I mentioned this in my "prologue"). The curious cenote pattern was what alerted the researchers to the presence of the structure -- later they found drilling records that confirmed the 3-D structure and the offshore circular extension of it.
This image is from the Shuttle Imaging Radar, which viewed the "rim" of the crater -- even though it's a only a couple of meters different from the rest of the surface.
Here's the 3-D structure of the impact feature, based on gravity mapping. The white line is the Yucatan coast:
