If you're hardcore, lab supply stores sell autoclavable tape that will adhere even when wet (even when autoclaved--surprise!) and can be removed with zero residue. This stuff is the de facto tape at any bio/chem lab, so if you have a friend who works at one, they should be able to snag you a roll.

It's not cheap on Amazon, but here's a link: http://smile.amazon.com/dp/B002VA5SEK

You could also just buy autoclave indicator tape and write on it; it usually has the same adhesive qualities.