A quote from the internationally-accepted precise open water swimming temperature scale, courtesy of loneswimmer.com:
Over 18°C (65°F): This temperature is entirely theoretical and only happens on TV and in the movies.

Last night, verified on three watches, we had 19.5ºC in Myrtleville. Wetsuits were abandoned up and down the beach.  Electrolyte transfusions were set up by the boathouse to help recover from the sweat.

Myrtleville – 22 July, 2013

Regular Myrtleville swimmers (known as Myrtlevillians to Mr. Bohane and others) had been sending home texts from their holidays crowing about 19ºC water “out foreign”.  They must be freezing.

After a committee meeting, it has been decided to rename the beach and a new sign was erected this morning:

Myrtleville – AKA Hot Water Beach

See you in the water!