Which set of conditions are required for the free communication effect?

• A. Open to the sea; partially flooded; Off centerline
• B. Open to the sea; fully flooded; On centerline
• C. Sealed; dry; Isolated
• D. Closed; partially flooded; On centerline

Answer: (A)

Free communication effect happens when water can move freely between spaces and with the sea, and there is a visible water surface inside the flooded area that can shift as the ship moves. For this to occur, you need an opening to the sea so water isn’t trapped, a space that is partially flooded so a free surface exists rather than a completely filled body of water, and the water mass positioned off the centerline so its movement creates a noticeable lateral moment. If the space is sealed or dry, or if it’s fully flooded (no free surface) or located on the centerline (less lateral effect), the free communication effect is minimized or not present.