Seelac was a Silurian. She was head of security on the Silurian ship, which was locked onto the SS Lucy Gray, when the last humans left Earth and tried to escape the solar flares.
The Eleventh Doctor and Amy Pond met Seelac when they entered the Silurian ship to find out why the SS Lucy Gray was so heavy. Seelac thought they were intruders and locked them up.
However the Doctor helped her and her people to protect the space ship from an asteroid storm. Seelac and Kestral, the leader of the tribe let them go.
When Seelac and Kestral met the humans on the space ship they tried to take the Doctor and Amy as a hostage to force the humans to work for them. However Captain Roy Calvert told them that the Doctor and Amy were strangers to them and that he wouldn't put his people in slavery for them.
Together with Amy the Doctor convinced Seelac and Kestral to work together with the humans and sail together through space. Seelac, Kestral, Tina Lockheart and Captain Calvert shook hands and made peace.
Only seconds after that a Dalek space shuttle crashed on the SS Lucy Gray. The Sulurian space ship fell back to Earth, together with all Sulurians. The Doctor managed to talk to Kestral, who told him that he and his people were okay and that they would find a way to survive. Furthermore he mentioned that a friendship between humans and Silurians wasn't ment to be. The Doctor told him that there would be another time when a friendship would be possible.