Jeremy Thomas’s review published on Letterboxd :
Piranha 3D was a big, gory and funny surprise when it hit theaters in the summer of 2010. The film was a rare example of a film that specifically aimed to be a big-budget B movie and did so while still satisfying. Unfortunately its sequel, Piranha 3DD, does nothing of the sort. With Alexandre Aja completely removed from the equation and a script from Feast and Saw IV through VII scribes Marcus Dunstan and Patrick Melton removing any sense of fun, this film barely even deserves the VOD and exceptionally limited theatrical release it has received. Director John Gulager's sequel lacks any real comedy, any sense of scares and weak performances from pretty much the entire cast.
With the script in shambles, spouting off nonsense abut the titular fish being confused by sulfur dioxide into following chlorine into a water park strip club, the one thing that Gulager could have done right is top the first film's gore level. But even that is beyond their skill level outside of a ludicrously creative way of recreating the most memorable kill in the first film. Cameos by Gary Busey and David Hasselhoff are entirely ineffective; only appearances by Christopher Lloyd and Ving Rhames conjures up any sense of fun. This is the first film with half the brain power and well less than half the enjoyment.