On January 23, 2007, about 1445 eastern standard time, a Ryan Navion, N4456K, registered to and operated by a private individual, as a Title 14 CFR part 91 personal flight incurred damage when the pilot attempted to make a precautionary landing at Marco Island, Florida. Visual meteorological conditions prevailed, and no flight plan was filed. The airplane incurred substantial damage, and the pilot was not injured. The flight was originating at the time of the accident. The pilot stated that after performing his preflight check, he took off on runway 17, established a climb, and retracted the landing gear. He said that the engine then started running rough, and he had used up about half of the runway, was too high for a normal flap landing, and there was a mangrove swamp beyond the runway, so he executed a "sharp" slip to the left. He said he then dropped the landing gear, but the airplane touched down before the landing gear locked. The airplane slid along the runway and veered to the right, impacting a VASI light, incurring damage. A postcrash examination of the accident airplane was performed by an FAA licensed airframe and powerplant mechanic, with an inspection authorization rating, and the examination revealed no anomalies.