Hi, I don't know which agency gave you your card, as it's not stated in your profile.
To get MSD cert, at least under SSI, you need :
1) To be AOWD. For this you need to have 24 logged dives under your belt and 4 specialties that qualify for Advanced. Nitrox IS NOT one of those as it requires no check-out dives. Also Underwater photo do not qualify, also Equipment Techniques. Specialties that do qualify are those that require check-out dives (2 dives each) Navigation, Boat diving, Deep diving, Dry Suit diving, Night & Limited Visibility diving, Wreck diving (the one you have), Search & Recovery, and some others.
2) To be Stress & Rescue diver. For this, not only to have taken that course, but also an EFR course and being active (EFR certification needs a revalidation every two years).
3) To have 50 logged dives under your belt with a total amount of 32 hours under water.
MSD (under SSI) is only a recognizance certification, a certification that shows that you have done all the above.
Boat diving is a specialty that is available, but no one requires that certification, as could be with night and/or deep. If you are going to dive in a place beyond 18 meters depth, the LDS should require your deep cert, also if you are going to dive at night. Also, no one will ask your navigation cert to do a particular dive, it's something for you how to know the way to return easily to the boat.
Another point is that (again, under SSI) there is no referral for specialties. Referral is only available for OWD check-out dives. Specialties check-out dives cannot be referred. This means that the one that gives you the course, is the one that will check your dives, no matter where. You can take the theory or classroom sessions at your home location and check-out dives in Cayman, but you need to go there with your instructor.
Finally, Rebreather diving is beyond Recreational diving. It´s normally under the XR (extended range) program or technical programs, with some more strict requirements.
All this is available in the particular standards that apply to your country or zone of each agency, which should be free to download in the web page of each agency (at least in SSI this is true).