Teams of cave divers coordinate efforts to collect samples for scientific researchers.
A vibrant world of black coral trees and sponges thrives on New Zealand's deep reefs as you descend beyond the level at which there is sufficient light for kelp to grow.
The rocky reef at 60 metres
The skeleton of an old black coral tree smothered in anemones - there's a lot of life worth investigating at 60 metres on the rocky reef in New Zealand.
Canterbury Wreck - the Operations Room
The ex-HMNZS Canterbury (F421) was deliberately scuttled in Deep Water Cove in the Bay of Islands in 2007. This is the Operations Room.
How did they form and why are they only found in one cenote in Mexico? This is the unsolved mystery of Hell's Bells, the crazy formations found in Cenote Zapote.