What is underwater GPS?

No. Standard GPS/GNSS signals cannot penetrate water. GPS relies on radio frequencies, which are absorbed almost immediately when they hit the water’s surface. As a result, GPS positioning only works in air, not underwater.

However, submersible GNSS receivers, like our Minipods are designed to:

• Withstand repeated immersion
• Resume accurate positioning as soon as they surface
• Provide seamless positioning for equipment that operates both above and below the waterline

This makes them ideal for hybrid marine operations where assets regularly surface.

In most marine contexts, underwater GPS navigation is a catch-all term that describes how operators track subsea assets when GPS is unavailable underwater.

In reality, this is achieved by combining:

• GNSS positioning at the surface, and
• Acoustic positioning systems underwater, such as USBL (Ultra-Short Baseline)

These systems work together to provide continuous positioning as an asset moves between surface and subsea environments.

1. Submersible GNSS (surface positioning)

Submersible GNSS devices provide precise GPS coordinates only when above the waterline. 

What is underwater GPS used for?

• Seismic source positioning
• Seismic streamer head and tail positioning
• Surface positioning of towed sensors in shallow water
• Surface positioning of ROVs, AUVs, USVs
• Subsea excavation vehicles
• Vehicle recovery operations
• Asset relocation
• Remote asset monitoring
• Tethered Diver Buoy

They do not transmit or receive acoustic signals.

2. Acoustic positioning systems (underwater positioning)

When an asset is fully submerged, positioning is achieved using acoustic systems, not GPS. These systems use sound waves to calculate range and bearing underwater.

Common technologies include:

• USBL (Ultra-Short Baseline) – vessel-mounted, fast to deploy
• LBL (Long Baseline) – seabed transponder arrays for maximum accuracy
• INS/DVL-aided navigation – dead-reckoning enhanced with acoustic updates

An underwater GPS tracker usually refers to a combined tracking solution, not a single device. It typically includes:

• A submersible GNSS receiver for surface positioning
• An acoustic positioning system for underwater tracking
• Software that merges both data sources into a continuous track

This approach allows operators to monitor location in real time, even as an asset transitions between underwater and surface environments.

MiniPod GNSS receivers allow accurate subsea-to-surface communication.