i've started going swimming regularly with some friends of mine. usually we get around going to the pool on tuesdays and thursdays, but it really depends on how busy people are, so we shift the schedule around... the pool itself is a medium sized public pool - there are showers, a dressing room and etc. apart for adults there are usually a lot of kids (around 12 y/o) who train there at the same time and cause a lot of havoc :-).
the length of a corridor is 25 meters and we usually end up doing at least 15 runs (or more) for one hour. the water contents may seem quite "chemical" for a newbie in comparison to salt water and its usually better to wear a hat and glasses (actually hats are obligatory), but people tend to get used to it very quickly. as a mostly "marine swimmer" (during the summer at least), i find it much more difficult to swim in these waters, but its very good for the musculature.
overall i cannot really recommend swimming over playing football / basketball or some other activity during the winter, but its really a great exercise, especially if you are a programmer and a swimmer at the same time...this might end up being really good for your body if you are really up to it (and if you sit in front of the PC at least 8 hours a day).
i usually go at night, so after the swimming session the night itself is a little bit exhausted, but very pleasant and fulfilling at the same time.