Keeping a first person view of the world, the Jet Ski was too much like running around on foot. It also had severe problems with communicating frame of reference when driving in one direction when looking in another. It was then replaced by the Airboat, which was more consistent with the Resistance-built theme, to address these issues.
The Jet Ski model can be found in the playable Half-Life 2 Beta files, but its textures are not finalized, like the Digger or the AirEx Truck. It is unknown if they were ever finished.
Two sound files for the Jet Ski are still present in the Half-Life 2 sound folders, in "sound/vehicles/Jetski", while thirteen files can be found in the playable Half-Life 2 Beta sound files, in the same folder. Those two sound files were recycled for the Scout Car.
A WC mappack map named "canal_jetski.vmf" was used for testing it.
The Machine Gun appears to be an M60, but in the Half-Life 2 Beta the Heavy Machine Gun is not an M60. This suggests that at one point, the HMG was an M60.