There is no regular monitoring of the ocean floor.  However, we do have the Argo buoys, which often extend down to 2000 meters below the surface.  There is also a new generation of "deep Argo buoys" but they are very limited in numbers right now (12 per year) because of funding. Caitlyn wrote a nice article on the Argo program here:  https://www.climate.gov/news-features/climate-tech/deep-argo-diving-answers-ocean’s-abyss