overboard

Sailboat missing since October found adrift, boater missing - Hawaii News Now - KGMB and KHNL Seeking information from sailing friends of Greg who may be able to provide information to his family about is sudden disappearance. Thanks.

A question for those of you who have (or had) chain lockers that drained overboard... Is the drain just a plain hole (i.e., a thru-hole)? Or, is there a 1-way valve inside to keep water from coming in through the hole? Or, is there a ball valve inside that would let you close the ability...