Systems and methods for converting marine current into electrical energy are provided. Certain systems include a housing with an opening that is adjustable between an open position and a closed position and a plunger that is configurable between a porous state and a non-porous state. The plunger can be configured to translate about the housing in a first direction when the opening is in the open position and the plunger is in the non-porous state, and in the opposite direction when the opening is in the closed position and the plunger is in the porous state. Certain systems include an axis configured to rotate, decks extending radially from the axis, and a vane disposed between the decks. The vane can be configured to translate between a first end of the decks and a second end of the decks when the axis rotates one hundred and eighty degrees.