- ulcus
- uliginous channels
- ullage
- ultimatum
- ultra mare
- ultra vires
- ultra-zodiacal
- umbra
- umbrella-warping
- unattached
- unbend, to
- unbitt, to
- unclaimed, as derelict
- undecagon
- under bare poles
- under-bevelling
- under-bright
- under canvas
- under-current
- under deck
- under foot
- under level
- under-manned
- under-masted
- under metal
- under-run a warp, to
- under-run a hawser or warp, to
- under sail
- under-set
- under-shore, to
- under-skinker
- under the lee
- under the sea
- under the wind
- under-tow
- under way
- underwriters
- unicorn
- sea-unicorn
- unicorn-fish
- uniform
- union
- union down
- union-jack
- unlimber, to
- unlivery
- unmanageable
- unmoored
- unreeving
- unrig, to
- unroomaged
- unrove his life-line
- unserviceable ticket
- unship, to
- unwholesome ship
- up along
- up anchor
- up and down
- up-and-down tackle
- up boats!
- up courses!
- uphand-sledge
- uphroe
- upmaking
- upper counter
- upper deck
- upper finishing
- upper masts
- upper strake
- top-rider futtocks
- upper or top-rider futtocks
- upper transit
- upper-works
- up screw!
- up with the helm
- uranography
- uranoscopus
- uranus
- urca
- ursa major
- ursa minor
- usages
- ushant team
- utlaghe
- uvrou
- vacuum
- vadmel
- vail, to
- vakka
- vale
- valuation
- valued policy
- valves
- vambrace
- van
- vane
- vanes
- vane-spindle
- vanfosse
- vang