The data shown here, updated every half hour, indicates the channel current speed in miles per hour as well as direction.  Discussion with experts around the Great Lakes suggest that channel current speeds greater than 0.5 mph becomes dangerous to the novice swimmer, while speeds of greater than 1.75 mph can cause even the most experienced swimmers to become overwhelmed.  Remember that the data provided here is for informational purposes only and that swimming is not allowed in the Picnic Rocks area. is the U.S. government's official web portal to all federal, state and local government web resources and services.