Unit 1 was traveling North on the Stono River on auto pilot. As it neared the Stono River Bridge it began to veer to its port side in a slow turn. 

The operator of Unit 1 was asleep at the wheel. One passenger on Unit 1 tried to wake the driver but was unable to in time to alter course or speed. 

Unit 1 collied with Unit 2 at the St. Johns Yacht Harbor floating dock just South of the Stono River Bridge. The bow of Unit 1 ramped onto the deck of Unit 2 and became stuck on a mooring post on Unit 2.

Stono River