The S.S. Minnow is the name of the ship the seven castaways were traveling on when they got beached on The Island. The Minnow was a small ship the Skipper was captain over (with Gilligan as his first mate), and he used it to give "three hour tours" to people around Hawaii (with free lunches). During one of the tours, there was a huge storm that swept the Minnow and it's passengers out to sea after which they drifted for a few days and eventually got beached.
In the episode, "Goodbye Island", the Professor tried to make nails to patch up the holes in the Minnow but failed. Then, later, Gilligan and Mary Ann found tree sap to substitute for syrup which turned into a hardy glue. However, right after patching up the holes with the glue, the glue ceased sticking and caused the Minnow to completely fall apart.