Lidl has shown interest in the Hunton Bridge site which sites next to the M25 junction 19 and 20.
Lidl has sent in an application for a premises licence and is currently in the process of completing plans which will then be sent to Watford Borough council for approval.
For now no deal will be struck until plans get accepted.
The business is estimated to be worth millions.
A Lidl spokesperson has confirmed to have exchanged contracts on the World of Water site on Watford Road, Kings Langley.