Nice capture. I think I would have cropped tighter on the bottom and possibly a little on the left and right to bring the swimmer more into the foreground.
nice photo. I think it would have looked better if you would have raised or lowered the subject just a bit. Being dead center, the subject doesn't look like they are going, or coming.
I think swimming photos really require being able to see the swimers arms. If he's doing the butterfly, then capturing the picture when the arms are fully extended to the sides is much more dramatic.
Perhaps I will mention rhe obvious a splash of fill flash would have lifted this image to a higher level. So if you were miles away with a 500mm tele and xtender diregard this remark, 8. hope this comment helps .