The SSS Esperanto was a designated "ocean seeding ship" featured in "Back to Reality", the last episode of Series V.
Its three-year mission was to explore deep space and locate potential S3 (or Earth-like) planets that were covered by ocean, introduce primitive life-forms to these extraterrestrial environments and finally speed up the evolutionary process. Her mission was successful; indeed, it was off all predicted charts — on one ocean planet the Esperanto succeeded in causing five million years' worth of aquatic evolution in just three solar years.
The SSS Esperanto crashed onto the ocean floor when it was attacked by one of the creatures she had helped create: a gigantic squid-like creature whose ink had hallucinatory and despair-inducing properties. The ink caused all the crew of the Esperanto, and even a stray fish, to have hallucinations which made them despair and commit suicide. The fish committed suicide by voluntarily closing its own gills.
It is revealed that, of all the ocean-dwelling species the Esperanto created, the giant squid had either eaten them all or caused them to die with its despair-inducing ink, leaving the ocean devoid of life except for the squid.
When Starbug found the Esperanto, the crew were also attacked by the squid and had a bizarre but elaborate group hallucination which led them to believe all their experiences on Red Dwarf were nothing but a video game, and their real identities to be people whom they all despised. In their hallucination, a brummy technician named Andy says that to kill the squid they were supposed to use the SSS Esperanto's laser cannons, citing the name "Esperanto" as a clue (Esperanto means "one who hopes", and hope defeats despair).
Holly destroys the despair squid with limpet mines. After surviving their hallucinations, the Dwarfers leave the empty hulk of the Esperanto behind on the now lifeless ocean floor.
The Esperanto was used as the background for the Red Dwarf Series V DVD cover.