An oscillating water column turbine (100; 300), comprising: a shaft (101, 301) configured to rotate about a central axis (103; 303); first and second annular ports (112, 114; 312, 314) disposed about the central axis; rotor blades (120; 320) coupled with or integral with the shaft (101; 301) and disposed between the first and second annular ports (112, 114; 312, 314); a flow passage (104; 304) extending between the first and second annular ports (112, 114; 312, 314), the rotor blades (120; 320) intersecting the flow passage (104; 304); and a shut-off valve (124; 414) including first guide vanes (116; 316) and second guide vanes (118; 318), the first guide vanes (116; 316) disposed proximal the first annular port (112; 312), the first guide vanes configured to control a first fluid flow into the flow passage (104; 304), and the first guide vanes including first fixed guide vanes (116F; 316F) and first movable guide vanes (116M; 316M), the second guide vanes (118; 318) disposed proximal the second port (114; 314), the second guide vanes configured to control a second fluid flow into the flow passage (104; 304), the second guide vanes including second fixed guide vanes (118F; 318F) and second movable guide vanes (118M; 318M), and the first and second movable guide vanes (116M, 118M; 316M, 318M) are configured to rotate about an axis perpendicular to the central axis (103; 303). a shaft (101, 301) configured to rotate about a central axis (103; 303); first and second annular ports (112, 114; 312, 314) disposed about the central axis; rotor blades (120; 320) coupled with or integral with the shaft (101; 301) and disposed between the first and second annular ports (112, 114; 312, 314); a flow passage (104; 304) extending between the first and second annular ports (112, 114; 312, 314), the rotor blades (120; 320) intersecting the flow passage (104; 304); and a shut-off valve (124; 414) including first guide vanes (116; 316) and second guide vanes (118; 318), the first guide vanes (116; 316) disposed proximal the first annular port (112; 312), the first guide vanes configured to control a first fluid flow into the flow passage (104; 304), and the first guide vanes including first fixed guide vanes (116F; 316F) and first movable guide vanes (116M; 316M), the second guide vanes (118; 318) disposed proximal the second port (114; 314), the second guide vanes configured to control a second fluid flow into the flow passage (104; 304), the second guide vanes including second fixed guide vanes (118F; 318F) and second movable guide vanes (118M; 318M), and the first and second movable guide vanes (116M, 118M; 316M, 318M) are configured to rotate about an axis perpendicular to the central axis (103; 303). the first guide vanes (116; 316) disposed proximal the first annular port (112; 312), the first guide vanes configured to control a first fluid flow into the flow passage (104; 304), and the first guide vanes including first fixed guide vanes (116F; 316F) and first movable guide vanes (116M; 316M), the second guide vanes (118; 318) disposed proximal the second port (114; 314), the second guide vanes configured to control a second fluid flow into the flow passage (104; 304), the second guide vanes including second fixed guide vanes (118F; 318F) and second movable guide vanes (118M; 318M), and the first and second movable guide vanes (116M, 118M; 316M, 318M) are configured to rotate about an axis perpendicular to the central axis (103; 303).