The ocean looks blue because water
absorbs longer-wavelength colors of
light more strongly than it does blue.
When the sun’s white light enters the
ocean, red/orange/yellow light dissipates
quickly, and mostly blues remain. That’s
why divers stop seeing reds around
depths of 20 feet, but blues last until
it’s too dark to see. SourceSource 2
The areas that were covered with thick ice sheets in the ice ages that ended some 12,000 years ago are covered with lakes and ponds of many sizes, many of which are a beautiful blue or green colour, though in the case of spotted lake (see http://bit.ly/29kJQzp) something more surreal can result.
Divers thought they found a real-life
Atlantis after discovering ‘pillars’ and
'paved floors’ off the coast of Greece,
but the strange rock formations were
actually created by concretion, a
natural phenomenon where cement
forms in the sediment when microbes
use methane that escapes from the
sea floor as a source of energy. SourceSource 2
A crowdfunding campaign for a product that claims to allow
humans to breathe underwater without the use of scuba equipment has
raised over a half million dollars so far. The Triton
— “artificial gills” that will work similarly to gills on fish —
supposedly allows swimmers to breathe underwater.