On August 25, 1998, at 2020 eastern daylight time, a Piper PA-23-250, N33MP, sustained substantial damage when it landed with the landing gear not extended at Grosse Ile, Michigan. The instructor pilot and another pilot receiving training in the accident airplane, reported no injuries. The dual instructional 14 CFR Part 91 flight was operating in visual meteorological conditions. No flight plan was on file. The local flight departed at 1920. The instructor pilot stated that while preparing to land the airplane, they were following another airplane landing in front of them. He said that when he heard the other airplane report on the radio that they were going to conduct a full stop landing, he prepared for a go-around. He said the other airplane was able to clear the runway in time for him to land and he changed his mind. He says that due the distraction he failed to lower the landing gear.