keel
structural element of a ship hull, or boat hull
drop keel
combination of ballast keel and centreboard
Winged keel
Keel type
swing keel
keel that can be swung up and down in flight with the boat
lifting keel
keel of a boat that can be shifted upwards and downwards
bilge keel
instrument
canting keel
sailing ballast that can be swung to windward