freediving is the real term. free diving is the word snorkelers use to make themselves feel special.
Apnea is a term people dont understand much, they think of sleep apnea and treat me like im dying, or just say WAAA!?!?.
Then again when I say freediving people think one of 2 things: skydiving (often they think its skydiving without a parachute. lol a one time sport

), or cliff diving.
when will people learn
EDIT: besides, calling myself a freediver makes me feel far more... professional then when I call myself an apneist or however you spell it.