During the Second Task of the Triwizard Tournament, the colony consented to hold the hostages that the Champions had to rescue in their village. As part of the agreement, their singing voices were used as part of a clue that the Champions would need to decipher. The Golden egg, which the Champions had to retrieve from a dragon in the First Task, contained a song that could only be heard when submerged underwater.
During the Second Task, the Merpeople attempted to stop Harry Potter from rescuing more than one hostage.
After Harry successfully rescued
both Ron Weasley and Gabrielle Delacour, the Merchieftaness spoke to Albus Dumbledore about the incident, and recounted his determination to see all the hostages to safety.The Second Task
Following the death of Albus Dumbledore in 1997, the Merpeople paid their respects to the Headmaster during his funeral, breaching the waves of the lake en masse and watching the proceedings.
Behind the scenes
In Lego Harry Potter: Years 1-4, the merpeople actually attack, whereas in the movie and book they only confronted Harry when he tried to take more then his own hostage, but even then they only threatened to attack.