Underwater Inspection & Hydrus AUV 3D Mapping | CMG Great Keppel Island

Middle Island Underwater Observatory Inspection

Client: DEMEX
Date: September 2025

Commercial Marine Group was engaged by DEMEX to deliver an underwater inspection of the Middle Island Underwater Observatory, located off Great Keppel Island in the Southern Great Barrier Reef.

Delivered in a remote marine environment, the works combined commercial diving, subsea excavation, structural inspection, and Hydrus AUV 3D imaging to assess submerged infrastructure and seabed conditions.

CMG’s integrated approach enabled accurate inspection and visual documentation of the observatory structure, ballast chamber, and surrounding underwater assets.

Scope of Works

CMG delivered a coordinated underwater inspection package including:

• Hydro-vac excavation to expose the base of the underwater observatory
• Ballast chamber inspection, drilling, and material sampling
• Underwater structural inspection of RSJ connections
• High-resolution underwater video and photographic capture
• Deployment of Hydrus AUV for 3D underwater mapping and site visualisation.

Hydrus AUV 3D Inspection Capability

CMG deployed the Hydrus Autonomous Underwater Vehicle (AUV) to capture high-resolution 3D imagery of the underwater observatory, piles, and surrounding seabed structures.

This approach enhanced traditional diver inspections by providing full-site visualisation, spatial context, and detailed subsea imagery, supporting clearer assessment of marine infrastructure conditions.

Project Outcomes

Across the project, CMG delivered:

• Detailed inspection of the ballast chamber and base structure
• Identification of ballast material and chamber configuration
• Confirmation of external RSJ structural connections
• Inspection and documentation of surrounding piles and shipwreck features
• Capture of 3D underwater imagery for asset assessment and reporting

Project Metrics

• Inspection completed over a 3-day offshore campaign
• 3 ballast chamber drill points completed and assessed
• Seabed excavation undertaken to expose critical structural interfaces
• Hydrus AUV deployed for full-site 3D underwater mapping
• Multiple subsea assets inspected, including observatory, piles, and surrounding structures

Project Significance

This project demonstrates CMG’s capability to deliver advanced underwater inspections using a combination of commercial diving and AUV 3D imaging technology.

The integration of Hydrus AUV enhances CMG’s capability to provide accurate subsea visualisation, improved data capture, and clearer marine asset assessment outcomes.

Sector

Marine Infrastructure | Subsea Inspection | Underwater Asset Assessment | AUV 3D Imaging