This was in about 1993. I decided that I could not live in Istanbul without swimming the Bosphorus. I went down to Bebek and asked a man with a Zodiac whether he would take me across and stay close to me as I swam back across to make sure I didn’t get killed by the massive amount of shipping. He took me to the cove just north of the Asian side of Fatih Sultan Mehmet Bridge. I jumped out and swam under the bridge to Rumeli Hisarı.
Later I was in a race that went from the Kanlıca Ferry Quay to Ortaköy. That meant swimming under both bridges and, because I didn’t know the currents at all, I ended up crossing the Bosphorus several times.
[1]