Originally Posted by The pokemaster
It is kinda hard to explain, but essentially, you follow the water currents etc until you reach the lab. After you come off the final current, go left underneath that current towards the shallow water. Go down and left, avoiding the currents, until you come to a clearing with a male swimmer swimming in a circle. There should be a small rock near where you came into the clearing. Go down from that rock, again avoiding the currents, and follow the little path. You should pass another swimmer, and wallah. :)
Also, if you struggle to find the path, mainly because of the amount of wild sprites pouncing and getting you confused, use a Max Repel... makes it much easier to find the path trough the rapids.