11th April 2026

NASAC launches nautical archaeology project to solve 100-Year-Old shipwreck mystery in Portsmouth

A new underwater archaeology project has been launched in Langstone Harbour by NASAC member, Riley Conway, to uncover the identity and story behind a century-old shipwreck, which coincides with Portsmouth’s landmark centenary celebrations in 2026.

Supported by a grant from Portsmouth City Council as part of the Portsmouth 100 programme, the initiative aims to shed light on a long-standing maritime mystery while celebrating the city’s rich nautical heritage.

The project focuses on a wreck believed to be the dredging vessel Withern, which sank in 1926 – the same year Portsmouth was officially granted city status. However, uncertainty remains, as another dredger, Witham, sank nearby in 1912 under similar circumstances. Both vessels were lost on their moorings in Langstone Harbour, and the true identity of the wreck has yet to be confirmed.

Sonar image of the wreck site. Credit: Martin Davies

Uncovering a Harbour Mystery
The wreck’s story is as intriguing as it is elusive. Historical accounts suggest the vessel sank overnight without crew, leaving behind unanswered questions about how and why it went down. With limited archival information currently available – including uncertainty over the ship’s age, captain, and final moments – the project team hopes modern survey techniques will provide long-awaited answers. Initial dives began on 9 and 10 April, marking the first step in a detailed and varied underwater investigation.

Divers prepare to explore the wreck. Credit: Charlotte Robinson

Innovative Survey Techniques
Led by Riley Conway, a member with the Nautical Archaeology Sub-Aqua Club (affiliated with the Nautical Archaeology Society), the project will combine recreational diving with professional archaeological surveying and recording methods. More information about the Club is available at: https://www.nauticalarchaeologysociety.org/dive-club

Key elements of the project will include:
• A full diver-led site survey using photography, videography and sketches
• Creation of a high-resolution 3D photogrammetry model
• Development of a virtual underwater tour
• A marine life survey documenting the wreck’s ecosystem
• Production of a short 2–3 minute documentary film
• Ongoing archival research into the vessel’s history

The findings will be compiled into a detailed written report and shared with local stakeholders, including Portsmouth Harbour authorities. 

Divers leave on the club RIB Honor to explore the wreck site

Funding Local Heritage
The Portsmouth 100 Community Grant Scheme, launched in November 2025, provides funding for projects that celebrate Portsmouth’s communities, culture, and heritage. More information about the programme is available at: https://www.visitportsmouth.co.uk/portsmouth-100/community-grants/.

This project exemplifies the scheme’s goals of fostering pride in local history while creating a lasting legacy beyond the centenary year. Grant funding will support essential operational costs, including boat fuel, maintenance, diver gas, and film production.

Community Impact and Legacy
The project is expected to benefit more than 500 residents by making Portsmouth’s underwater heritage more accessible and engaging. Outputs such as the 3D model, virtual tours, photography, and film will be retained by the City Council and made available for ongoing public access. By bringing attention to Langstone Harbour – often considered Portsmouth’s lesser known second harbour – the initiative aims to deepen public appreciation of the city’s maritime past.

A Personal Mission
For diver Riley Conway, who began diving in 2022 and recently joined the Nautical Archaeology Society, the project represents an opportunity to apply newly acquired skills in a real-world setting.“This project is about more than just a wreck,” he said. “It’s about uncovering a piece of Portsmouth’s history that’s been lost for 100 years and sharing it with the community.”

Looking Ahead
As Portsmouth prepares to celebrate 100 years as a city, the Withern/Witham survey project stands as a fitting tribute to its enduring relationship with the sea - combining heritage, science, and community engagement to bring the past back to life.