The Squalo is a cabin cruiser speedboat, built by Grotti in GTA IV and by Shitzu from GTA V onward, with roots in earlier GTA eras; it is due to appear in Grand Theft Auto VI. The boat shows up repeatedly in the second trailer and official screenshots, including two mounted on trailers outside Brian's Boat Works & Marina.
Vehicle data via GTA Wiki (Fandom), CC BY-SA 3.0.