The Air Whale by Matt Jones is a DIY project that you could complete at home. Made of garbage bags, it can be thought of as an ironic joke referencing the amount of junk the world dumps in our water.
The Air Whale cannot float in air on its own but it would look pretty rad if it were attached to something. It seems like an item Greenpeace would love and use at every ocean raid. The Air Whale has so many possibilities!