Time to do another tour/taxi after Atlantis submarine?

We are going to be in Grand Cayman on Celebrity, and the family booked a group excursion on Atlantis Submarine. The problem is the ship is scheduled to arrive at 10:30, the submarine is from 12:15-1:45, and departure is at 6:00. Do we have enough time after the submarine to do a Hell/Turtle Farm/Seven Mile Beach trip? If so, is it best to taxi out to those places, or will there still be any tour operators around the port at that time? If you think the answer to those questions is no, does anyone recommend what to do to pack as much into the stop as we have time for? I figure we can do any port shopping in the hour and a half before the excursion, but I'd like to see some other landmarks on the island after the sub. Thanks!

I'd get a taxi to Hell, and have them wait for the few minutes while you do the photo op and send postcards. Then, have them drop you off on Seven Mile Beach (Public Beach section if you have kids, Royal Palms if not) for some beach time. Grab another taxi back to the port afterwards.

If your departure is at 6pm, you really want to be in the tender line sometime just after 5pm (last tender is likely at 5:30). That doesn't really give you time to do the turtle farm too.

Or, do Hell and the turtle farm, and skip the beach. You will just find it tough to squeeze in all three.