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A Gato-class submarine (USS Peto) at the start of her long journey by drydock from Lake Michigan down the Illinois Waterway to the Mississippi River. There was no St. Lawrence seaway until the 1960's so the fresh water submarines had to be transported down the Mississippi River. Gato class submarines had a minimum draft of 12 feet but could be transported through Chicago and the 9-foot-deep Chain of Rocks Channel near the confluence of the Mississippi and Missouri Rivers by carrying the submarines in a floating dry dock. Robalo made her way to the Gulf of Mexico down the Illinois River to the Mississippi River to the Gulf of Mexico then on to Gulfport, Mississippi where she was refitted with reinstalled periscope shears, periscopes, and RADAR masts which had been removed to clear bridges over the Illinois River when it was transported through Chicago.