Sail Skills - ColRegs Free Guide to ColRegs (the International Regulations for Preventing Collisions at Sea, the IRPCS or Collision Regs).  Guidance covers all aspects with animations, pictures and diagrams.  Aimed at small vessel users but suitable for professional mariners.  Especially recommended for RYA examination candidates.
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Rule 23 Power-Driven Vessel Underway  Animation: under 12m ColRegs Home>ColRegs>Lights & Shapes>Animations>Power-Driven Underway>Power Under 12m - Sailing Vessel of power-driven vessels under 12m underway Power-driven vessel underway under 12m based on a sailing vessel (a ketch) “propelled by machinery” showing an all-round white light instead of  masthead light and sternlight back to top Power-driven vessel - a bulk carrier Power-driven general Power-driven vessel under 50m - a passenger vessell Under 50m Power-driven vessel under 12m - a motor cruiser Under 12m Power-driven vessel under 7m & 7kts - an excursion boat Under 7m and 7 knots Air-cushion vessel - USN hovercraft WIG craft (Russian) Air-cushion WIG A passenger boat under 50m and a RFA Lengths of vessels