've also read that because you are working out in the water you don't burn as much because your body tried to hold onto fat because of the lowered temperature. This may be a pure myth,
The number of calories you burn is going to have a lot more to do with your heart rate than the temperature of the water.
Also, you burn more calories in colder water, because your body has to work harder to stay warm.
And finally, most gym pools aren't cold enough to make that much of a difference either way.
A lot of people don't feel like swimming is as hard a workout because you don't feel yourself sweat when you're swimming. I'll admit that I have to fight that feeling as well - for me part of a good solid workout is the pouring sweat at the end of it.
So when I don't sweat (or can't feel myself sweating) I sometimes feel like I'm not working out hard enough.
But I've worn my heart rate monitor into the pool before and I know when I'm swimming laps, that I do get my heart rate up there and I do burn calories. In fact because I don't swim a lot (I'm a good swimmer, but it's not something I do all the time), I often get my heart rate up higher, faster when swimming laps than when I'm on the elliptical or treadmill. I find it harder to maintain a steady pace while swimming and wind up over working myself quickly.
As far as feeling like you're flailing around - I usually start out pretty well, but feel like I'm flailing by the end.
I suspect it's just like the elliptical, treadmill, whatever - it'll take you a few weeks to get into a groove. I know the first few times I used the elliptical I felt like I was going to fall forward and felt like I looked ridiculous - it took me a couple of weeks to get into the groove of it.