A bill to extend and increase the authorization for winter navigation on the Great Lakes-Saint Lawrence Seaway System.

Amends the River and Harbor Act of 1970 to extend the demonstration program for winter navigation on the Great Lakes-Saint Lawrence Seaway System until June 30, 1979 (presently expires December 31, 1976). Increases the authorization for such program from $9,500,000 to $15,968,000.