In terms of elevators and water, there is a reason to be cautious, but phobias are beyond sensible reason. In this sense, I don't think those phobias are all that different from agoraphobia which I perceive as a fear of panic attacks caused by leaving your safe zone.

Hopefully you can pinpoint what exactly it is the lies behind your agoraphobia and that would help you explain it better. Only on a few occasions had I panicked upon going outside, but those were highly anxious times where I wanted to avoid being seen or times when I knew I was going to a location where I had them before. I noticed that anxiety of certain places had a lot to do with the feeling of being 'stuck', such as in certain social situations and in classrooms. That fear made me anxious and the inability to escape would give me anxiety attacks. In that way, I was conditioned to fear certain locations or scenarios.