What Nivek said...the Dive Bus cruise program is set up for self-diving. The only problem I see with that is your schedule. The Dive Bus closes around 5-ish. So two dives might be difficult. They're such nice people though that they would probably make arrangements for you to drop the tanks in the yard though if necessary.
Cruise Ship Passengers
My other suggestion is to check with Caribbean Sea Sports. Because a boat dive with them is a possibility also within your schedule. A couple days a week they offer a 2:30PM
boat dive. They also do a Wednesday Sunset trip if there's 6 signed up. Tuesday they do a Night
shore dive on their house reef. And guided shore dives on demand on their house reef during the day also. CSS is at the Marriott Emerald Beach - 2? miles north of the cruise port in Piscadera Bay. It can't be a
five minute ride from the cruise port. (Note - it's not the Marriott Renaissance adjacent to the cruise port.)
Caribbean Sea Sports Curacao - Pricelist & Boat Schedule 2015
Another advantage to CSS is that if you wanted to do some other diving elsewhere - maybe rent a car? - since IMO the best shore dive is
not at CSS.
our equipment rental is open 24 hours so you and your buddy can simply gear up and go exploring on your own.
I believe that's for walk-ins as well as resort guests but check to be certain. The people I know that've done that stayed at the Marriott.
Renting a car opens up a lot of good diving options both north and south of the cruise port. Some locations are going to pretty much shut down around 5PM so getting a cab to pick you up would be more iffy than I'd want to try with a cruise departure time looming.
For reference the cruise port is next to Superior Producer on this list - actually so close that your ship being tied up will close it for diving that night.
Scuba Shore Diving Site Listing for: Curacao, ABC Islands Once you get farther south or farther north, there's a decided lack of street signs/places to ask directions - GPS advised.
Realistically with a car just about all the sites are options.. I might steer clear of #'6-7 after dark since they closed/razed the former Sunset Waters dive resort so it's a lot more deserted now. Possibly #4 also as you could wait for a long time for someone to show up if you had car trouble - one of few sites with no facilities immediately nearby. A repair vehicle would probably be from town - that could be the better part of an hour.
Another option is to check with Atlantis Diving and see what they can do.
Atlantis Diving Curacao - Cruise ships They'll pick you up. They're a little closer to the cruise pier than the Dive Bus.