An apparatus for recovering a core from an undersea formation. A coring tool adapted for being connected to a drill string includes a coring bit for recovering the core from the undersea formation. A catcher has a closed state for sealing the core in the coring tool. A retainer retains the collapsible catcher in an open state, and an actuator applies suction to the coring tool. The applied suction serves to move the retainer to allow the catcher to collapse for capturing the core, such as by releasing flexible fingers of the core catcher from a telescoping liner associated with the retainer. Related methods are also disclosed.