The most common freedive-specific statistics that freedivers track:
Best Performances ("apnea" means "without breath")
Dry static apnea time (DSA)(seconds) - staying still, not in water
Dry dynamic apnea time (DDA)(meters) - walking at a normal pace on land
Wet static apnea time (WSA)(seconds) - staying still, face-down in contained water
Wet dynamic apnea, no fins distance (DYN)(meters) - swimming horizontally underwater
Wet dynamic apnea, with fins distance (DNF)(meters) - same as above
Constant Weight, no fins depth (CWT)(meters) - straight down and up with out dropping any ballast.
Constant Weight, with fins depth (CNF)(meters) - same as above
Something to think about... These are the personal stats any freediver is going to track. There are others which are competition only, so I left them out.