Scientists on Florida's Gulf Coast are trying to find an underwater robot that has mysteriously vanished.

The robot from the Mote Marine Laboratory in Sarasota has been missing since Monday.

It cost about $100,000. It also was equipped with a detector to find red tide, a toxic algae bloom. That was valued at another $30,000.

Scientists aren't sure what happened to the robot, which is nicknamed Waldo. It could have had a leak or malfunction and sunk to the bottom. It also could be on the surface, but its communication system isn't working properly to signal its location.

The lab hopes boaters out for the busy Labor Day weekend might spot Waldo.