The best thing was the Sea Trek tour through De Palma tours in Aruba. We walked underwater with huge helmets that kept our hair dry and let you breathe normally. It was AMAZING. Note: They provide dive booties for your feet. Go with the larger group -- you get more time underwater.
We took an independent taxi tour - quite enjoyable and a lot cheaper than the shore excursions. The island is impoverished, but beautiful. While the port markets were nice, the spices were fresher on the tour.
Took an independent tour to the fort. It was a bit of a struggle to negotiate for a taxi that had AC, a reasonable number of people in it and the right price. I had to walk away from one tour that promised eight people but then tried to stuff in 10.