I think there is plenty of low-hanging fruit left... under the water. We have barely skimmed the surface and know more about the galaxy outside of our planet than we do about the kilometers of ocean right underneath the surface. Once we start to look at the ocean more, once we master better diving and camera technology... I feel like we'll be able to discover a number of very interesting things. The ocean is just too huge for there to not be surprises there for us to experience.