Thanks for the reply Clyde! I was able to get your model working with Gazebo Garden - I had someone explain to me the difference between gazebo classic and ignition. My problem was that I didn’t have the colcon packages installed to build properly.
For anyone just starting with a project and not sure about the workspace environment on your device this may help. If you want to use the Gazebo Garden you should follow the source install instructions here: Gazebo. Be sure to double check any of the export commands that they are for your device file system. The basic file system should look like home/colcon_ws/src/bluerov2_ignition and if you git cloned the ardupilot_gazebo repo onto your home location home/ardupilot_gazebo - check the export commands in Clyde’s github above may clear things up.