SonarBuddy is made and published by
TUDOR ST JOHN MARSDEN-HUGGINS.
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published on the App Store.
About SonarBuddy
SonarBuddy is a navigation app developed by TUDOR ST JOHN MARSDEN-HUGGINS.
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App Information
SonarBuddy is freely available from the App Store. The app size is 1,003.00 kB. The latest version available is 1.1. The last update was on October 30, 2026.
Technical Requirements
The app has a content rating of Everyone. The app has been available on the App Store since October 2026.
Description by TUDOR ST JOHN MARSDEN-HUGGINS(from the App Store)
Charts are often wrong where cruisers go: anchorages, passes and reef-strewn approaches. Your depth sounder already measures the truth on every passage. SonarBuddy collects those measurements, quietly and automatically, and shares them with the cruising community.
HOW IT WORKS • Join your boat's Wi-Fi and pick your chartplotter. B&G, Simrad and Lowrance plotters are found automatically; PredictWind DataHub and other NMEA 0183 sources work too. • Tap Start logging. SonarBuddy records depth and position in the background, even with the screen locked or while you use your navigation app. • Logs upload automatically whenever you have internet, at anchor, in port or later.
THE COMMUNITY MAP • See where boats have actually sounded, drawn in white over the seabed model. • Measured depth contours and per-cell depths, from real soundings. • Spot where boats measured less water than the charts or seabed model show, before you get there. • Check a route: get the distance, and see whether it crosses places where community soundings differ from the model.
ANONYMOUS BY DESIGN Soundings appear on the map without your name or boat. Each passage gets its own random ID. You choose whether to share your boat with people you know.
HELP WHEN YOU NEED IT The built-in help assistant can see what the app tried on your device, such as connection attempts and errors, so it can help you get connected without error codes or guesswork.
Try it without a boat: choose "Demo (simulated passage)" when picking your plotter.
SonarBuddy is an invite-only beta, starting in Fiji. Join the waitlist at sonarbuddy.com.
NOT FOR NAVIGATION. SonarBuddy shows community soundings and a free seabed model for planning and awareness only. Always use official charts, allow for tide and your own draft, and keep a proper lookout.
Each subscription will automatically renew 3 days before the expiration date for
the same time period. Subscriptions can be cancelled at any time before the renewal.
