All my hobbies growing up involved water...swimming, fishing, duck hunting, and wake boarding, so I'm pretty comfortable in the water. I don't dive, but I have no qualms about swimming in deep water. I don't wake board anymore, but I duck hunt and wade fish along the TX coast quite a bit. The only thing I'm afraid of when I'm out hunting or fishing is stepping off into a pocket of deep marsh mud. It happened to me when I was 19, and I was fishing along. I sank up to my waist in the mud, and the water came up to my chin. If I had panicked, I would have died that day. It took me 2 hours to inch my way out of the mud, but I did it!
I never wade fish in soft mud anymore. If it doesn't have a hard sand surface, I don't fish it!