Louth Bay is a town and locality in the Australian state of South Australia. It is named after the bay named by Matthew Flinders on 26 February …Louth Bay is a town and locality in the Australian state of South Australia. It is named after the bay named by Matthew Flinders on 26 February 1802 which itself is derived from a place in Lincolnshire. At the 2006 census, Louth Bay had a population of 408.