why leg cramps when swimming?

First time I've been swimming in yrs.  The water was 72 degrees (an underground spring) and the air was 80.  Took me a long time to inch my way in as it felt cold, but when submerged it felt fine.

after an hr, where I stopped for a long period to talk to someone, my toes cramped up and I had to use my  hand to unbend them, then shortly after my calf got a cramp, so I was afraid to be swimming and I was tired and ready to leave anyway.

My legs were tired from a long hike the day before.  Would that have been why they cramped, or was it the cool water?  Or maybe using different muscles than hiking?

you might have had lower than normal potassium levels because of your previous excercise. a lack of potassium in your muscles can cause cramping.

Cramps are hard to understand.  Some will get them when dehydrated (I do), others swear by keeping electrolyte levels up (calcium, potassium, etc).  There are "sport leg" pills that are basically calcium and magnesium, but they don't seem to do anything for me.

When I do masters' swimming, I will usually start cramping up on kick sets or flip turns after about 50 minutes, regardless of everything else.  I think being tired contributes.  Never had a problem with cold water (though our pools only go to 78).

ok, thanks.  Normally I eat a banana every day, but haven't lately.  Also, hadn't drank any water yet.  Will try to do both next time.