On dry land, in this part of the world, the standard hand-signal used to indicate sexual intercourse is to show the OK sign with the left hand while inserting the index finger of the right hand through the hole in the 'O'...

Someone has pointed out to us that scuba divers round the world use the OK hand signal to indicate that they are 'all right'...So there may be an exception in that case, depending on who you're with underwater and what your real intentions are..:^)

And also, in Turkey (and in many places in Europe, as you may already know) one uses that hand-sign to make reference to one or another of two body orifices -- not your mouth, not your nose, not your ears....

And, be careful about the game of 'stealing the nose' of a Turkish child or friend...The thumb inserted between the index and middle fingers is the way you 'flip the bird' or 'give the finger', in Turkish hand-language...