Complex sentence: Following his return, Meen organized a proper expedition with the cooperation of the National Geographic Society and the Royal Ontario Museum, which travelled to the site in a PBY Catalina flying boat in July 1951, which enabled them to land on nearby Museum Lake.
Split into simpler sentences: Following his return, Meen organized a proper expedition with the cooperation of the National Geographic Society and the Royal Ontario Museum. They travelled to the site in a PBY Catalina flying boat in July 1951, landing on nearby Museum Lake.