The Monarch Sun was one of two ships that sailed from Florida to the Bahamas in the mid 70s for a couple years before going out of business. The other one was named the Monarch Star and regularly sailed to Nassau. Below is a photo that was in the Chip Guide.
To find the history of these two ship go to the link. This started out as the Argentine, was built in Pascagoula, MS shipyards, sailed as a Commodore Cruise line and met it's demise off the coast of Massachusetts. While sailing as the Monarch Sun, the captain committed suicide on one trip and a subsequent trip it ran aground near Cuba and nearly 300 passengers had to be rescued.

https://en.wikipedia.org/wiki/SS_Argentina_(1958)