Thanks for the post, it could have been dehydration for sure that day.
Duchess,
I am not a doctor! But what you wrote sounds excatly like dehydration to me. From personal experience only I can tell you that when I have dehydrated the following occured: No sweat, racing heart, feeling of weakness, dimmed vision and a few times - passing out. Also I have experienced similar problems when mixing the pool with other excercise.
Not sure why the pool seems to do that to me, but I long ago made sure I did not swim on the same days I do other exercise.