Answer: scubadive

AnswerCrossword Clue
SCUBADIVEVisit the Andrea Doria, say
SCUBADIVEGet in way over one's head?
SCUBADIVEGo deep, in a way
SCUBADIVEExplore with a tank
SCUBADIVEExplore underwater
SCUBADIVEExplore a reef
SCUBADIVEExplore a coral reef, e.g.
SCUBADIVEExplore a big wet bottom?