@BobGriest ,
I couldn't access your map via the URL you provided, but I noticed one of your other posts where you shared another link that I could access:
If that is the map that you are working on, I can see that you are using data that is published by NOAA. The bathymetry data in your map is coming from an image service which contains raster data.
ArcGIS Online Analysis capabilities include raster data management tools. To use tools such as Extract Raster you need to have a ArcGIS Image for ArcGIS Online license. If I understand you correctly, you want to export the data to use in your 3rd party application HomePort. Unfortunately, I don't have enough knowledge about this application to help you with loading data into it. Additionally, it looks like this application is discontinued?
To export the bathymetry data from the image service, you can try to use the Export capability with the REST API: https://gis.ngdc.noaa.gov/arcgis/rest/services/bag_bathymetry/ImageServer/exportImage . Below is an example of how you can export the data to multiple image formats:
With the parameters above I have exported a tiff image that covers your area:
You mentioned the .gpx and .adm file formats, which are normally used for data such as routes, tracks, and waypoints. Again, I'm not familiar with the HomePort application, but I don't think you can use bathymetry data with these formats. If you want to create routes, tracks, and waypoints in the .gpx format, you can use the Features To GPX tool in ArcGIS Pro.
Paulina