srsly guys, plz help!
If you are talking about the Sea Mauville (formerly Abandoned Ship), it is located to the east of Dewford Town on Route 108 near the end and a little to the north part of the Route.
If you are talking about S.S. Tidal you can access it by going to Lilycove or Slateport but only if you have an S.S. Ticket with you which you get after completing the Delta Episode from Norman in Littleroot Town.
Hope I helped! :)))