The best stuff to see is usually not very deep so don’t see the need to get higher certifications. My wife and I have dove all over…
Great Barrier Reef, Bora, Fiji, Roatan, Belize, Cozumel, all over Hawaii, Grand Cayman, Aruba, many of the Caribbean islands.
The Wall is Grand Cayman was very memorable. Barrier Reef was cool but a little disappointing. Roatan was spectacular. Koloa Landing is always fun because lots of turtles. Bora bora was a shark dive which was cool.