Sperm really needs to get in the vagina.
It is possible for the little blighters to get there from the labia, or if they happen to drip down after anal sex (gross I know).
But given how many have recently asked that if it was on their big toe, or knee or thigh, then no they can't swim that good.
Even from the vaginal opening they have a long haul to get to their destination.
Most sperm meet egg in fallopian tubes so its a few inches of vagina, find way through cervix, swim round uterus, find map, look for fallopian tube, hope egg isn't coming down other one instead.
Seriously it is a wonder we ever succeed in getting pregnant.