Bay seniors who would like to get away from it all without leaving town, might want to consider floating weightless in a dark tank for an hour at Zazen, a massage and yoga center located in of all unlikely places, the Tenderloin. It’s billed as sensory deprivation, a way to meditate free of distractions, lolling in water which has been combined with 1500 of pounds of Epsom salts. The tank is 8’x6’. No recommended for claustrophobics. $70.