Obviously I'm the only person who can't swim!
Not at all, my times are only so close because my half marathon time is faster than most. My swim is slow.
I think I've just tried to make a mental note to work on my swimming, where I've always said before I wouldn't bother. It would be an interesting motivational thing to try and PB in my half mara time in conjunction with keeping my swim time say 10 mins less than that.