Mer-Posters

Mer-Posters were a dangerous type of muttation appearing in the 98th Hunger Games. Able to breathe underwater and disguise their faces as those of loved ones, these beasts were not friendly in the slightest.

98th Hunger Games
Mer-Posters appeared in the 98th Hunger Games, tormenting Rebekah with the disguise of Alec. This lured Rebekah to them, where a mer-poster grabbed the girl and dragged her underwater. The monster nearly drowned Rebekah, but Jemima managed to rescue Rebekah just in time.

Appearance
They were described as having the bodies of mermaids, with the top half disguising as a loved one. They kept their lower portions hidden beneath water to further trick tributes.

Trivia

 * Their name, Mer-Poster, is a play on words of mermaid and imposter.