Deep scuba diving using compressed air is definitely to be considered a high-risk dive. All international diving organizations recommend limiting diving with compressed air to -40 meters of depth to avoid incurring what is called nitrogen narcosis. Compressed air is denser as the depth increases, and consequently greater breathing effort is required which could lead to breathlessness and greater air consumption.

In this collage of videos made in two different dives a few days apart but always in the same stretch of sea we filmed one of the many species of ctenophores that inhabit our Mediterranean Sea, from some research it seems to be the Bolinopsis infundibulum or tentacled Ctenophore.  ...

Underwater decompression consists of a series of steps or stops at a certain depth that the diver must undertake to desaturate his body ...