Under Keel Clearance in the Malacca and Singapore Straits Is Being Reviewed for the First Time in 50 Years

Why This Matters

On 27 August 2026, at the 49th meeting of the Tripartite Technical Experts Group (TTEG) on the Safety of Navigation in the Straits of Malacca and Singapore (SOMS), Singapore – supported by Witherbys and The Nautical Institute – formally launched a review of the Under Keel Clearance (UKC) requirement that has governed deep-draught transits through one of the world's busiest waterways since the 1970s. It's been designated TTEG Straits Project 16, with Singapore as project lead.

The Existing Rule, and Why It's Being Looked At

The current minimum UKC requirement in the SOMS is a fixed 3.5 metres – a static value set roughly 50 years ago, based on the hydrographic surveying, vessel design data, and navigational technology available at the time. Since then, hydrographic surveying accuracy, understanding of squat and dynamic draught, electronic navigation, and real-time environmental data have all moved on substantially, while traffic through the Straits has grown enormously.

Crucially, Witherbys and the review project itself are explicit that this is not a proposal to simply reduce the existing safety margin. It's an evidence-based question: using today's data and technology, does a single fixed value remain the safest and most effective way to manage UKC, or could a more dynamic approach do better on both safety and efficiency? Accident analysis in the high-density areas of the SOMS reportedly shows that collision risk considerably outweighs grounding risk in that traffic mix – and the existing fixed UKC requirement bunches deep-draught vessels into concentrated tidal windows, which is itself a collision-risk driver worth examining, not just a grounding-margin question in isolation.

What a Dynamic UKC Framework Could Look Like

A modern, risk-based approach to Under Keel Clearance Management (UKCM) can account for vessel-specific and environmental factors in real time – tide, swell, speed, squat, trim, and actual surveyed water depth – rather than a single number applied uniformly regardless of conditions. Malaysia specifically flagged the forthcoming IHO S-100 standard (replacing the current S-57 standard) as relevant here: S-100 is designed to enable real-time digital marine data into ECDIS. Malaysia also pointed to the IHO S-129 standard for Under Keel Clearance Management, which is built specifically to deliver real-time and predicted water-depth safety margins directly within ECDIS – a natural technical fit for the kind of dynamic UKC requirement this review is exploring.

What Each Littoral State Flagged

All three littoral states contributed specific technical concerns at the meeting:

• Malaysia emphasised that navigation and hydrographic requirements need to be built into the project from the start, tied to the S-100/S-129 transition.
• Indonesia raised sandwave movement – particularly in three key areas – as a factor that needs accounting for, and proposed a Joint Survey Research Programme to support the project.
• Singapore, as project lead, has requested input from both Malaysia and Indonesia to help develop the project's formal Terms of Reference.

Capt. Iain Macneil, CEO of Witherbys, described it in stronger terms than a routine technical update: “This is not just a once in a generation review, but a once in a lifetime review.”

What This Means for Bridge Teams Right Now

Nothing changes operationally yet – the 3.5m UKC requirement stands until this project concludes and any revised framework is formally adopted. But it's worth understanding the shape of what's being discussed, because a shift toward S-129-driven, ECDIS-integrated UKC management would be a genuinely different way of planning a Malacca/Singapore Straits passage than referencing a single static clearance figure against tide tables. If your vessel is already S-100-ready or moving that way, this is a concrete, near-term example of what that transition is actually for.

Test Your Knowledge

Think you've got this covered? Put it to the test in Crew Connect's free Knowledge Checker — try a quick navigation round and see how you score.

Related Reading

• ECDIS S-100/S-101 standards – what the wider transition actually involves