Question 1

On an ECDIS laminate/symbol sheet, the OOW is shown a symbol consisting of a red circle with a red cross through it. What does this symbol represent, and what action should it prompt?

Accepted Answer

It is the IHO chart symbol for a dangerous underwater obstruction or wreck with a defined danger — the OOW should treat the marked position as a charted hazard to be avoided, check the chart's associated text/notes for the depth or nature of the obstruction, and ensure the planned route maintains a safe distance from it, increasing the safety contour/depth margin if operating in the vicinity Standard IHO/ENC chart symbology uses circles and crosses (and combinations of them) to represent various dangers to navigation, including wrecks, rocks, and obstructions, with different symbol variants indicating whether the danger is considered to have a defined or undefined depth, and whether it is dangerous to surface navigation. A red circle with a red cross is one such danger symbol, and an OOW being shown this on a laminate identification sheet is being tested on basic chart symbol recognition — a foundational ECDIS/chart-work skill. The correct response to encountering such a symbol on a real chart during passage planning or while navigating is not just to recognise it, but to treat it as an obstruction to be avoided: check any associated notes, soundings, or text describing the hazard (depth, nature, whether it is "PA" position approximate or "ED" existence doubtful), ensure the planned route gives it adequate clearance, and if navigating near it, consider increasing the ECDIS safety contour setting so the system itself provides additional alerting if the vessel approaches too closely. The examiner in this scenario was checking general symbol literacy, since a candidate who cannot recognise basic danger symbols on sight may not reliably notice them during real passage planning.

Question 2

You're preparing a passage plan for a coastal leg in a yacht drawing 3.2m. At one point the chart shows a least depth of 3.8m at chart datum. What MUST you check before finalising this leg?

Accepted Answer

The tidal height at the time of transit to confirm sufficient under-keel clearance Charted depths are referenced to chart datum (often LAT), so you must add the predicted tidal height for your transit time to get the actual depth, then compare to your draft plus a safety margin to confirm UKC.

Question 3

During your watch the ECDIS gives a "safety contour crossing" alarm. What is the correct response?

Accepted Answer

Assess the situation against the planned route and charted depths, take action to maintain safe water, and inform the Master if there is any doubt A safety contour alarm indicates the vessel may be approaching water shallower than the set safety contour. It must be investigated against the route and charted information, with avoiding action taken and the Master informed as appropriate — never simply silenced.