Suggestions for afternoon plans once finished with morning dive.

[Tmaxx1]

My cruise ship gets into port in Georgetown @ 7am and leaves at 4pm. I am planning on getting off the ship and walking to Eden's Rock dive shop for a Discover Scuba dive. The dive starts at 9am and lasts 3 hours until 12pm. Once we are done with the dive at 12pm, we will probably get a quick bite to eat and then look for something else to do before the cruise ship leaves at 4pm. Is it feasible to catch a cab to 7 mile beach and spend a few hours there? I am guessing it's probably only a 10min cab ride there, right? What time is recommended to leave the beach and head back to the cruise ship?

Thanks.