Maelstrom, Mine, Moat, Mouth, Narrow, Narrows, Notch, Opening, Orifice, Outlet, Pass, Passage, Passageway, Pit, Pore, Quarry, Ravine, Reach, Reflux, Regurgitation, Rent, Rift, Rime, Road, Roads, Rupture, Seam, Separation, Shaft, Slit, Slot, Slough, Sound, Space, Split, Stoma, Strait, Straits, Swirl, Trench, Twirl, Valley, Void, Vortex, Wadi, Well, Whirl, Whirlpool, Workings, Yawn, Maelstrom, Abyss, Aperture, Arm, Armlet, Backwash, Backwater, Bay, Belt, Breach, Break, Broaching, Canyon, Cave, Cavity, Chap, Chasm, Check, Chimney, Chink, Clearing, Cleft, Col, Couloir, Cove, Crack, Cranny, Crater, Creek, Crevasse, Crevice, Cut, Deep, Defile, Dell, Depth, Dig, Diggings, Disclosure, Ditch, Donga, Draw, Eddy, Estuary, Excavation, Fault, Fiord, Firth, Fissure, Fistula, Fjord, Flaw, Fontanel, Foramen, Fracture, Furrow, Gap, Gape, Gash, Gorge, Groove, Gully, Gut, Hiatus, Hole, Hollow, Incision, Inlet, Interval, Joint, Kloof, Lacuna, Leak, Loch