The impulse to swim at night always reminds me of Paul Bowles' magnificent novel, The Sheltering Sky - and in particular a passage where Kit finds herself, at night, looking into a garden at a wide pool, surrounded by graceful palm trees:
"She stood staring at the calm dark surface of the water; straightaway she found it impossible to know whether she had thought of bathing just before or just after seeing the pool..."
Her swim becomes a revelation:
"She stepped out into the moonlight and waded slowly toward the center of the pool. Its floor was slippery with clay; in the middle the water came to her waist. As she immersed herself completely, the thought came to her: 'I shall never be hysterical again.' That kind of tension, that degree of caring about herself, she felt she would never attain them any more in her life."
From Paul Bowles' The Sheltering Sky. (Photograph by Alexander Chow-Stuart)