Zimmerman was last seen on April 9, 2005 in Freeport, Texas. He and two other men, Austin Childs and David Keller, went on a fishing trip on the Gulf of Mexico in Zimmerman's 28-foot pleasure craft. They took a yellow Laborador Retriever dog, several 160-quart ice chests with white snap-on cushions, an orange life ring, a blue and red raft, and three standard-sized orange life jackets on their boat. The men were expected to return the following day, but they did not and they have never been heard from again.

The men's boat was later found capsized in the ocean. It had a two-foot hole in the bottom; officials believe the boat accidentally ran into something, possibly a log. A seat cushion and three life jackets were floating nearby. There was no sign of the men at the scene, and an extensive search turned up no trace of them.

Childs, Keller and Zimmerman are presumed lost at sea. All three are from Houston, Texas.