Underwater Air Lift Bags Enable Historic Shipwreck Recovery in the Baltic Sea

Underwater Air Lift Bags Enable Historic Shipwreck Recovery in the Baltic Sea

Project Overview

Location: Baltic Sea (55°N, 18°E)

Depth: 92 meters

Operation Period: June 2023

Lead Organization: Nordic Marine Recovery Group

Equipment Used:

Four 20-ton capacity underwater air lift bags (corrosion-resistant neoprene with Kevlar reinforcement)

ROV (Remotely Operated Vehicle) with precision buoyancy control

Acoustic positioning system

Challenge

Recover a 17th-century merchant ship's 8.5-meter bronze cannon (estimated weight: 3.2 tons) without:

1. Damaging the fragile wooden wreck site
2. Exposing divers to prolonged decompression risks
3. Disturbing the sediment-encased artifact

Solution Implementation

Phase 1: Preparation

• ROV pre-installed specially designed lift bags with soft slings around the cannon
• Each bag rated to 150% of required lift capacity for safety redundancy

Phase 2: Controlled Ascent

• Sequential inflation maintained 0.3 m/s ascent rate
• Real-time monitoring via strain gauges on load straps

Phase 3: Surface Transfer

• Artifact suspended in water during transfer to conservation barge
• Maintained constant seawater spray to prevent oxidation

Results

✅ Successful Recovery: Cannon lifted intact with zero structural damage

⏱ Time Efficiency: 47% faster than traditional crane-based methods