Creating a height map of the seafloor

[HudoGriz]

Anyone willing to share their practices on creating a seafloor height map?
I am thinking about creating a collage of real-world data (just like for the surface), and then eroding it, but have no ideas what kind and order of erosion to apply
My current map is a 8 bit grayscale of the surface relief and the water is marked as black.

[Redrobes]

If you take real world data to collage then presumably you wont need to erode it as it will have been done so already.

On another point - I would try to use 16 bit or even float format for any height map. Although I guess bathymetry would not be so important as normally you might render the sea on top I think its generally a good idea to use a higher precision format for any heights. That, and you will almost certainly find that downloadable data for bathymetry will be in 16bit format anyway. If I recall correctly, the NOAA data is public domain because its US gov data but you need to make sure to read their licenses.

https://ngdc.noaa.gov/mgg/global/global.html