Hi @TheIntern, welcome to the forum 
The BlueOS Water Linked DVL extension supports using the DVL A50 as a source of rangefinder data, but ArduSub does not currently have terrain hold/tracking built in.
I’m aware that @clyde has worked on implementing that, but I’m not sure how well it works or how close it is to being merged in. It looks like that pull request is waiting for reviews at the moment, so I’ve raised it internally in the hopes we can keep things moving on it