Not true. Oreopithecus was a bipedal hominoid with a precision grip who was adapted to an aquatic setting for at least 2 million years on the isolated island of Tuscany-Sardinia in the Mediterranean.

Harrison & Rook, Function, Phylogeny, and Fossils: Miocence Hominoid Evolution and Adaptations. 1997

“The remains of Oreopithecus bambolii are extremely abundant in VI, and this species represents one of the commonest mammals at the site…..Evidence for a primarily aquatic setting and a humid forested environment is provided by the extensive lignite accumulations, the common occurrence of skeletal remains in anatomical connection, the abundance of fossil crocodiles, chelonians, and freshwater mollusks, and the occurrence of otters…..The area was evidently poorly drained, and the forested areas were interspersed with numerous freshwater pools and shallow lakes. pg 335

“Interestingly, there is also a corresponding decline in the abundance of Oreopithecus in V2, which might simply imply a relatively narrow ecological preference by this taxon for swampy, forested habitats.” pg. 336

“Another possibility is that Oreopithecus was exploiting aquatic or wetland plants, such as water lilies, reeds, sedges, cattail, pond weeds, horsetails, and stoneworts, all of which are abundantly represented in the pollen spectrum from Baccinello.” pg. 341,