- ignorance
- iguana
- iland
- ilde, and ile
- ilet
- illegal voyage
- immer
- immersion
- imp
- impedimenta
- import, importation, and importer
- impossible
- impost
- impregnable
- impress, to
- impression
- impressment
- imprest
- imprest-money
- in
- in and out
- in-board
- in-boats!
- in-bow!
- inch
- incidence, angle of
- inclination
- inclination of an orbit
- inclinatory needle
- inclinometer
- incompetency, or insufficiency, of a merchantman's crew
- indemnification
- indemnity
- indented line
- indented parapet
- indenting for stores
- indentures, pair of
- index
- index-error
- index-glass
- index-rod
- indiaman
- indian ink
- indian ocean
- indraught
- induced magnetism
- indulto
- inequality, secular
- inertia
- infantry
- inferior conjunction
- inferior planets
- information
- ings
- in-hauler
- initial velocity
- injection-pipe
- inland sea
- inland trade
- inlet
- inner and outer turns
- inner jib-stay
- inner stern-post
- inner post
- innings
- innis
- inquiry, court of
- inshore
- inshored
- inside muster-paper
- inspection
- instalment
- instance court
- institution
- instructions
- instrument
- insufficiency of a merchantman's crew
- insurance
- insured
- insurer
- intact
- intensity of light
- intercalary
- interest policy
- interloper
- intermediate shaft
- internal contact
- internal planking
- internal safety-valve
- interrogatories
- intersection
- intertropical
- interval
- in the wind
- intrenchment
- inundations
- invalid
- inver
- investment
- invincible