Est. by Captain Ivan Martsynenko
The Mariner's Open Book of Knowledge
Practical seamanship, navigation, safety, and engineering — written by seafarers, for seafarers. Free to read, open to contributions.
Watch on YouTubeCharted waters
Browse by discipline
Navigation & Seamanship
Chartwork, pilotage, passage planning, and bridge watchkeeping.
ExploreCOLREGs & Rules of the Road
International Regulations for Preventing Collisions at Sea.
ExploreSafety & SOLAS
Life-saving appliances, fire safety, drills, and SOLAS requirements.
ExploreCargo Operations
Stowage, lashing, stability, and cargo documentation.
ExploreMarine Engineering
Main and auxiliary machinery, bunkering, and engine room practice.
Start courseMaritime Terminology
Glossary of nautical terms, abbreviations, and standard phrases.
ExploreDynamic Positioning
DP systems, vessel station-keeping, operator training, and emergency preparedness.
ExploreFrom the logbook
Latest entries
Introduction to Tides
A practical seamanship lesson on tidal forces, spring and neap tides, tidal datums, streams, the Rule of Twelfths, and safe use of tide predictions.
How a Bow Thruster Works
A practical lesson on tunnel-thruster reaction, drive components, blade pitch, installation, safe operation, maintenance and low-speed limitations.
Marine Boiler Maintenance: Cleaning, Blowdown, Gauge Glass and Burner Care
A video lesson with study notes on water washing, tube cleaning, soot blowing, boiler and scum blowdown, gauge glass blowdown, burner maintenance and furnace defects — with two step-by-step simulators and a 36-question self-test.
Centrifugal Separators: Purifiers and Clarifiers in the Engine Room
How the disc-stack centrifuge keeps fuel and lubricating oil fit to burn — gravity discs, water washing, sludge cycles and the purifier-versus-clarifier decision.
Dynamic Positioning: Systems, Operations & DPO Training
An introduction to vessel station-keeping, the four core parts of a DP system, the DPO certification pathway, and opportunities to improve training.
IMO MSC.1/Circ.1580: Guidelines for Vessels and Units with Dynamic Positioning (DP) Systems
The current IMO guidelines for DP vessels and units, approved by MSC 98 on 16 June 2017, superseding MSC/Circ.645 and introducing the DP Verification Acceptance Document.
Knowledge grows when it is shared
Officers, engineers, and cadets are invited to join as editors. Write what you know — someone on a night watch needs it.
Become an editor