This is the Bonus Cache for the Gloucester Docks Adventure Lab Cache.
Please do not attempt to find a physical container at the headline coordinates for several reasons 1) You are not a submarine 2) You will get wet 3) It will probably result in a visit to the local hospital/police station or worse 4) THERE IS NO PHYSICAL CONTAINER THERE
To find this cache you will need to complete the short walk around Gloucester Docks in the Adventure Lab app, upon completing the 5 stages you will be given the final coordinates for this cache which is hidden a short distance away.