It is crazy how cold the water is in fact. One time I went to this beach that we go to fairly often on a hot day in summer and they had floated this kinda huge, I dunno, bouncy castle type thing with slides and stuff about 50m out from the beach. There were boats to take you to the thing and you had to pay for a ride... I thought fuck that, I'll just swim it, and then I got into the water and was almost paralyzed with cold. The 50m distance was completely insurmountable, it might as well have been a thousand miles wide canyon, I swear no human alive could have made it.
Some of them near Setubal seem to be a bit warmer though, or maybe I'm slightly used to it now.