The Marlin was added on 4 - 06 - 17 with an update that featured it and three other new animals. Like the narwhal when it attacks some one with it's pointy bill it draws blood and attracts sharks. It is currently the farthest evolution you can get along with others such as the orca and polar bear. It is extremely fast, in fact it is one of the fastest in the game currently.
Photo Credit - http://vdsmaza.com/movie-video/deeeep.io-new-animal