IRPCS – Lights: Vessels Making Way (Rule 23 & 25)

Understanding and identifying navigation lights is a crucial part of staying safe at sea and complying with the International Regulations for Preventing Collisions at Sea (IRPCS). This crib sheet focuses specifically on vessels making way—those that are underway and moving through the water under their own power, sail, or other means. It’s designed to help you recognise which lights different types of vessels display while making way, understand how their configurations indicate a vessel’s type, size, and activity, and commit key patterns and exceptions to memory. Whether you’re preparing for an exam or improving your night-time recognition skills, this guide simplifies what can feel like a complex topic, so you can approach it with confidence both in the classroom and on the water.