Shallow water blackout is a loss of consciousness caused by cerebral hypoxia towards the end of a breath-hold dive in water typically shallower than five metres (16 feet), when the swimmer does not necessarily experience an urgent need to breathe and has no other obvious medical condition that might have caused it. It can be caused by taking several very deep breaths, or hyperventilating, just before a dive. Victims are often established practitioners of breath-hold diving, are fit, strong swimmers, and have not experienced problems before.
Samba is a loss of motor control. It is a partial loss of physical or mental integrity and generally occurs up to 15 seconds after reaching the surface, normally during your first breath after a dive. It happens due to not having enough oxygen in your brain.
Watch this video on Sambas and Blackouts by Erez Beatus an AIDA Freediving Instructor and Judge, Former Freediving Coach for Israel and Former Freediving World Record Holder.
Thankyou and credit to the North Shore Underwater Club and Erez for this essential and valuable safety video.