Dick, the distinction that Greg described is the commonly accepted one. For additional clarification, check The Gaming Table. You will find a section titled "At Sea", which inclues the Cruise Line/Cruise Ship chip names. In contrast, the riverboat casinos are listed under each state/city location. Names are conveniently cross-referenced.

A few ships can be confusing, in cases where a ship moves from one state to another...or converts from international-water cruising to an in-state day cruise status...without issuing new chips. But those cases are infrequent.

While we're on the subject of classifying chips, there's occasional confusion about how to list chips from Indian reservation casinos. For convenience, I list them within the state where they are physically located. However, those Indian reservations techically/actually are sovereign Indian nations within the USA but SEPARATE from the state they are within. If you want to be totally accurate, Indian casinos would not be listed within any of the 50 states, but instead in a separate category.