Gravel Barge Through Locks

A powerful tug pushes a fully laden gravel barge through the Ballard Locks.

As the barge is almost the width of the lock (and has a large draft underneath as well), the dynamics of the water are quite interesting as the tug tries to move the barge.  A strong current rushes backwards to fill the gap being made behind the barge, and the tug then has to work against this current.