Minimum depth below keel required for effective DP ops

Hi Mariners,

I have a question for all DP ops mariners on the forum. What is the minimum depth where you can get effective positioning of the vessel using DP? Any information on operational restrictions, etc. are welcome. Assume muddy seabed and a swing down thruster at the bow in addition to tunnel thrusters, and azimuths at the aft. Experience with Voith Schneider props would also be good to hear…