On Sunday:

Location: Porto (and the beach on Leça)
Temperature: around 25ºC
Water Temperature: warm enough to be able to stay in without feeling cold.
Time between setting foot on Portuguese soil and being inside the Atlantic Ocean: 19hrs (possibly my personal record)
Pride at having been able to accurately predict that it was a good beach day and that the water would be warmer than usual: priceless.

On the downside I went to the beach with surfers who managed to find the only beach in a 10km stretch that had proper waves which obviously meant that the sea was too rough for proper swimming. However we compensated by having a slap-up barbecue with two kinds of fresh grilled fish (average price £3 per kg), corn (which I discovered is better than the one you get in Britain), peppers, white Port, etc