Lee is right.  Our basic water sports suits (Breeze from OS Systems) run
$385. Add to that a $240 custom charge and then double it (for you and
your wife's suits) and you have paid for the pool heater and a couple of
years of electric bill.

Water aerobics only works if you are having fun and stick to a regimen.
 If you use a wetsuit or drysuit you will still have cold feet, hands
or head and will no longer be having fun.  That will make it too easy to
quit.

I live in the cold Northwest and have seen a couple of private pools up
here where they have put up a nice metal building over the pool and deck
area and have a retractable roof to open for the summer month (yeah ...
it IS the Northwest!).  You might think of investing in that as well.

Just a thought.