The vehicle stopped working while on the causeway.
It has now been marked with a pink buoy and Jersey Coastguard said the obstruction should be removed when the sea goes out.
The next Low Water times in St. Helier are at 21:14 tonight and 09:57 tomorrow (Friday 5 March) morning.
“Mariners transiting the area should do so with caution, keeping a sharp lookout,” officials warned.
