Since 1 October 2003, the Marine Liner has been operated by JR West 223-5000 series EMU trainsets. The first car on most Takamatsu-bound trains is a JR Shikoku 5000 series bi-level cab car with reserved seating. Previously, 213 series EMUs were used.
From Okayama to Takamatsu, all Marine Liner trains stop at Chayamachi, Kojima and Sakaide. Most trains also stop at either Senoo or Hayashima, or both. Some early morning and late evening trains make additional stops at intermittent stations on the Seto-Ohashi and Yosan lines.
As it is classified as a "Rapid" (快速 kaisoku) service, a standard fare is charged for using the Marine Liner. It currently takes about one hour to cover the entire journey. A passenger may upgrade to reserved seating for an additional fee.
A crew change for the train driver and conductor occurs at Kojima, the boundary station between the two operating railways.
The Marine Liner runs over two sections known collectively as the Seto-Ohashi Line. The Okayama-Kojima section is operated by JR West1, and the Kojima-Takamatsu section is operated by JR Shikoku2.