Q. I have limited or no access to open water. Do I really have to practice in it?
A. Yes, you need to swim in open water regularly. The only way to practice open water is in open water and all those articles telling you otherwise are lying. If it’s fresh water, train in fresh water, if it’s sea water, train in the sea.
-- Swimming for beginning open water swimmers and triathletes is like planting a tree. Twenty common beginner triathlete questions answered.
I was thinking about this very thing this morning as I was doing my training for an open water swim next week.
You have no idea how glad I am that I wasn't dumb enough to ignore this advice. Swimming in open water is very different from swimming in a pool. You think that black line doesn't mean much or do much for you, but it totally does. It gives you a line to follow. The dimensions of the pool mean that you have a very clear idea of your progress (judging distance when your eyes are about an inch above the water is a lot harder than you think!). You get a groove on in the pool that you don't in a strange environment. You'll deal with temperature differences. You deal with how you breathe differently until you get used to the chill. I'd say that a wetsuit doesn't make as much of a difference with this as you'd think, except I have no idea. Never wore a wetsuit before. You might be dealing with the fact you can't see the bottom.
I was kind of startled by this today in my training. I swim in a lake that's murky green starting about a yard down, mostly. Which is fine. I knock my imagination unconscious for the duration of the swim and don't worry about it, knowing I'm in a lake where wildlife is considerably less of a danger than waterskis. (Yes, I train with a kayaker beside me. I am not entirely an idiot)
But the funny part was when we were moving closer to shore to stay away from motorized vehicles. I look down, thinking, "What the hell is that?" only to realize it's just leaves and I can see the bottom of the lake.
But while you can work on fitness and technique in a pool, the reality is that Loneswimmer is so very right. Training for an open water event without getting in the open water is foolish. The conditions are very different and you need to be able to cope comfortably. An event is the wrong place to find out how you deal.