Learn to Swim
Don t start swimming in moving water
If you're learning to swim in a river, you'll need to be more aware of the motion of the water. If you must learn to swim this way, make sure you're with someone who knows what he or she is doing,
After for In
I may be able to go after a week.
I may be able to go in a week.Or: I may be able to go in a week's time.
When speaking of a period of time in the future, use in, and not after. Here in means after the end of.