It is a new type of transportation that the Marlin truck driver drives instead of his regular mechanical version.
Like the bubble boat, the bubble tow truck has a cushion to step on for acceleration resorting the driver in a standing position. The entire tow truck is made of bubbles from the steering wheels, engine, and even the towing hook, which somehow tows Mrs. Puff's heavy boatmobile without popping. The truck tractor is rectangular and has two small circular headlights in the front.
Role in episode
After Highway Speed Patrol pulls over and confiscates Mrs. Puff's boatmobile because bubble boats became so popular that regular boats became outlawed, the Marlin truck driver comes in and tows away Mrs. Puff's boat.