This is next to Santiago. I visited up by Antafagasta and Iquique, the Pacific ocean felt uncomfortable cold, even in late summer (February). I got into the water during some downtime in Iquique just to say that I did. But the water was so miserably cold on that 82deg day, that I immediately got back out and headed back to the hotel and its nice pool.
According to NOAA, Iquique waters have an annual mean of 18C (~65F)
Santiago area looks to be about 15C (~59F)