So, I took that swim cap to a local sports memorabilia store to have the autograph authenticated. Turns out it's an authentic signature! So, now I have an authentication certificate with it. The guy said he has never seen an autograph on that particular swim cap before. Unfortunately, they don't do value of memorabilia. I went to ebay to see if things like that are worth anything. And all I found was a few caps worth about $4 and a few worth $600 and not one person had bid on them, so really that means it's worth nothing!
But seriously, I am really stoked to have this in my growing swimming collection! Thank you so much!