PD6 appears to be a group of ASCII messages; PD6 info here: https://waterlinked.github.io/dvl/dvl-protocol/#pd6-protocol-tcpserial
The specific device the customer has is here: https://www.waterlinked.com/dvl/dvl-a50?__hstc=138920684.070f7673144696095697e2da19c62c33.1671622550980.1671622550980.1671622550980.1&__hssc=138920684.1.1671622550980&__hsfp=981838616&hsutk=070f7673144696095697e2da19c62c33&contentType=standard-page
There are a few other DVLs that use this protocol, here's some info about a QPS driver that reads PD6: https://confluence.qps.nl/dm/network-ixblue-phins-dvl-halliburton-sas-pd6-standard-30-35590092.html
Got another request for this: https://hypack.atlassian.net/browse/SUP-3809