Because I don't think we've had a watersports prompt for this pairing yet. I want Anakin to pee his pants. The details don't matter too much, maybe it's something they planned or maybe Anakin just didn't listen to Obi-Wan when he told him to use the 'fresher before they left and now he is really regretting it. Anything is fine, as long as Anakin is very very desperate.

Bonus for Anakin crying and being super embarrassed, because not only is he about to pee his fucking pants but he is also sort of turned on by it. Also definitely would not be opposed to him begging.