My low blood pressure (90 over 50) is fine while I am under water but I notice when I get to the surface, my blood pressure drops suddenly and recently lost my vision for a second. Can anyone advise strategies on preventing black out and is my low pressure is an advantage or a concern? It feels like an advantage will I am down because my personal best is 3 mins and 10 seconds with out formal training (I am a newbie) but sure don't want to black out regularly or it might be dangerous.