Thalassa was a duo, established especially for the national selection of the 1998 Eurovision Song Contest. The duo excisted of Dionyssia Karoki and Yiannis Valvis. They won the national selection and could thus represent their country. However, this didn’t really go smoothly. Valvis had so much trouble with the organization, that in the end they forbid him to even enter the hall, because they were afraid he might ruin the show. He watched the show in his hotel room.
After the contest, Dionyssia and Yiannis went their own way.