#13 was my primary Water Polo cap number in high school athletics during Freshman- Junior year. Water Polo/Swimming was one of the most fun experiences I've had during my four years attending high school where I got to meet great people and swim around elbowing (and being elbowed) people.
Unfortunately I don't have the cap with me (school property which is pretty pricey for a set of caps), but they let me have the ball that was used to score my last goal (I wasn't much of a scorer since my primary duty was mainly ball control/passing) so that was a cool thing to keep.
I actually still use it whenever I go to the pool/beach mainly to play catch. Also got some nifty HS Water Polo/Swimming apparel throughout the years and even a signed photograph from a certain Olympic Silver Medalist (still holds swim records at the HS) who visited his old highschool (probably for a photo op) too.
Edit: oh I still got my team speedo (you don't want to see that do you?) and swim cap at least
So yeah #13 was my cap number so remember that since it will be on the test.