[Surprise Bart! Kon's actually been shoved into a pool and seen this supposed future he lives. So the t-shirt dig? He gets it and just huffs. Conner is so lame.]

Uh huh.

[Bart, Bart, Bart, Bart. Kon just sighs and now that he's properly collected himself he explains.]

Because when you get too close, you go out cold. I tried it after my powers came back when I arrived. Ended up crashing into a faceful of water. My friend did the same, she tried to swim it but no dice, she washed up. Even Supes can't get through. You lose your powers for a while after it aswell. So I wouldn't try unless you wanted to slam into an invisible wall and spend even longer at normal speed.