I think it's important to map our (in the Global sense) undersea conditions over time. We hear a great deal about Global Warming - yet it's only the timelapse satellite imagery that concretes it for dismissive minds.

The same can be said for coral reefs, rivers, etc. 'Coral bleaching' is a real problem and reflective of global weather events.

Regarding #2 - In a more idealistic vision of 'Underwater Google Maps', the Voyager Project [1] made an interesting plea to Google to do something similar and provide HD video feeds from UAVs [2].

[1] http://www.underseavoyagerproject.org/

[2] http://www.youtube.com/watch?v=P4iDQsXIi3I

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Edit - Additionally, existing 'undersea documentaries' tend towards visual hyperbole (ooh a yellow fish, damn sharks are scary, etc) - rarely exploring the topography of the ecosystem they're covering. Being able to wander aimlessly underwater may prove more valuable to a student's imagination and provide a more lasting feel for far flung places and culture (or the life of a crab) - as apposed to from a TV, the deck of a cruise ship, or a car window.