A bar has a charted depth of 0.8m. Your yacht draws 1.6m. At what minimum height of tide above chart datum can you cross, and what additional safety margin should you apply?

A. The draught alone determines crossing depth — subtract 0.5m from the draught for the required tidal height

B. Minimum tidal height needed: 1.6m (draught) − 0.8m (depth) = 0.8m above chart datum. Apply a safety margin of at least 0.5m for wave action and prediction error: therefore cross at HW−1h when tidal height ≥ 1.3m above datum

C. Charted depth of 0.8m means the bar dries 0.8m — it can never be crossed

D. Cross at any state of tide — charted depths include a built-in safety margin

A. The passage plan need only identify the destination — diversion decisions are made in real time

B. A port of refuge provides a safe haven if conditions deteriorate. Suitability factors: accessible in the expected conditions (depth, bar, height of tide); distance from passage track; available facilities (fuel, medical, communications); whether it can be entered at night; holding ground if anchoring is the only option

C. Any port on the chart is automatically suitable as a refuge regardless of conditions

D. Ports of refuge only matter for vessels without an engine — sailing yachts can always divert

A. A point on the passage (headland, strait, harbour bar) that can only be safely transited within a specific tidal window — the departure time and speed must be calculated backwards from the tidal gate time to ensure arrival within the window

B. Tidal gates only apply to vessels over 20 metres in length

C. A tidal gate is another term for a tidal stream atlas symbol on the chart

D. A lock gate at a tidal harbour — only relevant to inland waterways