The thing is most pollution and changes in the ocean are not visible right away, while hiking or on land in general I directly see consequences of littering and environmental impact and its possible to act upon (littering on highways)

in the oceans on the other hand a lot of environmental impact is just not visible, thus it needs to be made visible, I see a nice beach... I don't see particles floating just under the surface, I don't see the destroyed eco systems by trawling, I don't see "death zones" where there is no marine live...

so this is a good step into direction making these things visible