I modified ArduCopter for the APM 2.6 to run on the BlueROV. This has had much less testing than the current version and doesn’t have all of the features of the current ArduSub for Pixhawk. This code was basically just a proof of concept, and I don’t plan on developing it any further. The APM code is here. I think it will work with the current ROS package, if it doesn’t try this. Depth hold won’t work with the Blue Robotics depth sensor (without some minor modification to the code), this was tested with an MS5803. My suggestion is that you can try using this with your ROV, but you should get a PixHawk if you want support, features, and reliability.
-Jacob