I live in Kailua Kona Hawaii. We are fortunate in that we have a relatively pollution free ocean right nearby. The water is warm even in mid January 2018 by anyone but our won standards so barring the monthly jellyfish (box) bloom or a south swell, it's almost always available for a swim.
In addition though our county government here (the are no city level governments in Hawaii) has placed a priority on recreational activity for residents and visitors. Our county pools are "free" to all (paid by our local taxes) and open year round save for the occasional cleaning days or swim meets.
It's a matter of priority is all. If it's convenient for more people, they're far more likely to engage in the activities. If it's work or a bother (long drives, dirty pools, crowded lanes etc.), they'll just blow it off.