I am not an environmentalist. I am a conservationist. Scuba led to me becoming more aware of marine conservation issues and sustainable fishing issues. That said, I see a ton of bunk related to environmentalism and water issues. Some environmentalist org recently said 50 percent of coral reefs in the caribbean died off last year. I laughed after reading this report.
My first open water dives were in the caymans. I asked the guy leading the trip if spearfishing was allowed in the caymans while we were standing in line in customs in grand cayman. He took time and explained to me how few fish there really were (such as grouper) in the cayman diving areas and how few spear fishers would decimate the population. I heard him, but I didn't understand what he meant until I got into the water. Fishing is fine, but not every area can sustain it. If someone shoots the few big groupers on the top of the walls, nobody else will get to see them. And thus my mind started thinking more and more about marine conservation.
Divers don't necessarily have environmental concerns, but I think diving in different areas really opens a person's eyes. I remember diving in St. Lucia and lack of any fish over 4 inches due to local fishing. Read stories from people who try diving Jamaica and see the blight too much fishing has caused. Then read stories from people who dive in well managed areas where the fishing is regulated and enforced.
Almost every recreational diver believes somewhat in conservationism whether or not its in the forefront of their mind since they typically buy tickets to belize, the bahamas, the caymans versus the areas blighted by overfishing. They make a decision that they prefer conservation even if they don't realize it.
PS: I hate hippies.