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 27 Vessel Restricted in Ability to Manoeuvre  Animation:  at anchor ColRegs Home>ColRegs>Lights & Shapes>Animations>Restricted Ability Manoeuvre>At Anchor Vessel restricted in ability to manoeuvre based on a buoy service vessel at anchor back to top of vessels restricted in ability to manoeuvre A vessel recovering a navigation mark - restricted in her ability to manoeuvre A small vessel engaged in diving operations A vessel engaged in underwater operations where an obstruction exists A vessel engaged in mine clearance operations General requirements Operations with obstruction Diving operations smaller vessels Mine clearance