I went swimming in an indoor pool last Wednesday and did 5 lengths before feeling in need of a breather, then did 16 lengths altogether and felt good after it.
Friday I went into the outdoor pool, same size, on a hot and lovely day. it was cold getting in but it was lovely once past the first - ooh- feeling. However after 2 lengths I needed a breather and only managed 12 lengths in all, and felt really quite tired after it.
Brian suggested that cold water is harder to swim in because the water is sort of thicker, more dense as it is colder. It seemed to make sense but has anyone any idea if there is any real reason why it seemed harder work swimming in the outdoor pool? It has been puzzling me.