Can Grace safely pass between North Molle Island and South Molle Island?

Grace may be able to pass between the islands, but safe passage depends on her draught and the exact route. Mid Molle Island lies between North Molle and South Molle, creating separate passages with different hazards, so identify the intended gap on a current, detailed nautical chart first.

Identify the gap

A route through charted water around the islands is different from a close shortcut between their shores. The names North Molle and South Molle alone do not define a navigable track.

Open the largest-scale chart available and locate all three islands. Trace the intended route from approach to exit, checking:

• Whether it passes north or south of Mid Molle.
• The shallowest sounding and any drying areas along the whole track.
• Reef edges, isolated rocks and restrictions on either approach.
• Enough width to turn away without crossing another shoal.

The gap between Mid Molle and South Molle includes shallow, drying ground. Visible water does not prove that a yacht can pass safely. Nor does a tender crossing or another boat's track establish clearance for Grace.

Calculate Grace's clearance

Check Grace's loaded draught first. Her name gives no indication of how much water she needs. Use the figure for her actual keel or propulsion arrangement, allowing for cruising stores and equipment. On a motorboat, include the lowest part of the propellers, shafts, rudders or outdrive legs in their operating position.

The basic calculation is:

Charted depth + predicted tide height − loaded draught = predicted under-keel clearance.

For illustration only, a charted depth of 1.2 m plus a tide height of 1.5 m gives 2.7 m of predicted water. A yacht drawing 1.8 m would have 0.9 m beneath the keel before allowing for waves, prediction errors or other effects. These are example figures, not soundings for a Molle Islands passage.

For initial planning in sheltered conditions, allow at least 0.5 m beneath the keel. Increase that margin where the bottom is hard, the survey is uncertain or there is swell. A small calculated clearance over coral or rock is a reason to choose another route.

Check tide and stream separately

Use tide predictions for the location and date, applying any published secondary-port corrections. Check that the prediction's vertical datum matches the chart's depth datum, and confirm whether displayed times are local time or UTC. Queensland uses AEST throughout the year.