The most popular tridata sensors for sailing

January 28, 2026 • 5 min read

Learn how different sensor types work, and which is the best fit for your boat.

When entering a new harbour or anchorage, having someone on the foredeck to spot shallows makes the process a lot less stressful. Eyesight, however, is not a very reliable way to measure water depth and quickly meets its limits if you have a deep draft or if the water is murky. This is why most sailors rely on a depth finder as their trusted source of truth when entering unknown shallows. 

Out on the open water, depth matters less. This is when you care about your sailing performance. To understand your sailing performance, you need a speed through water sensor, a wind sensor, and a GPS to derive true wind and sailing performance metrics. 

In the past, it was common to have separate sensors for waterspeed and depth. However, every through-hull fitting in your boat is a potential water ingress point, so you should keep them to a minimum. 

An Airmar ultrasonic tridata sensor under a clean and freshly painted hull.

In an effort to reduce through-hull fittings, Airmar introduced the world’s first tridata sensor in 1984. This style of sensor grew in popularity, and since the early 2000s, integrated speed through water, depth, and temperature sensors have been the industry standard among sailors.

Tridata sensors deliver navigation-critical information, and reliability is a must. Read on to learn what type of sensors are available and which sensors are most popular among Orca boaters.

The big decision

Evaluating a sensor solution that covers speed through water, depth, and temperature can be complex. The big decision is whether to get a tridata sensor or individual sensors for the information you care about, and to make that decision, you should consider the following options:

• Mechanical or solid-state speed through water sensor

• In-hull or through-hull depth sensor

• Big brand or enthusiast brand

Mechanical or solid-state speed through water sensor

Speed through water can be measured with three different sensor types: paddlewheel, ultrasonic, and electromagnetic. Paddlewheels are the traditional and most common choice for cruising sailboats, while ultrasonic and electromagnetic sensors are solid-state alternatives with no moving parts. These solid-state sensors are more common on higher-end racing boats.

The Garmin GST 43 is a great standalone paddlewheel sensor.

Paddlewheel sensors are popular because they are simple, cheap, and easy to service. The drawback of paddlewheels is regular maintenance requirements and accuracy. Marine growth will slowly build up and eventually stop the wheel, so periodic cleaning is needed. Eventually, the moving parts will need replacement as well – so if you have a paddlewheel sensor, keep a spare paddlewheel at hand. Paddle wheels are also non-linear, meaning they need to be calibrated at different water speeds before they deliver accurate readings.

The Airmar DX900+ electromagnetic tridata sensor delivers both speed through water and leeway data.

Ultrasonic and electromagnetic have no moving parts. They are low-drag and largely maintenance-free. Ultrasonic sensors measure water flow using sound waves, while electromagnetic sensors use induced electrical fields. Both are attractive if you prioritize low maintenance and high-accuracy readings with lower calibration requirements.

In-hull or through-hull depth sensor

Depth can be measured using either a through-hull or an in-hull sensor. If you want a full tridata setup, this choice is effectively made for you – accurate speed through water requires a through-hull fitting. Most sailboats made since the early 2000s have an existing fitting for a through-hull sensor, so this drawback is a non-issue for most boaters.

In-hull depth sensors are installed inside the boat and shoot soundwaves through the hull. Their main advantage is avoiding the through-hull fitting below the waterline, which makes a DIY installation simpler. If you have an old boat without an existing fitting, you want a lower-risk upgrade, and can sacrifice some accuracy and depth range, this can be a good alternative.

Installing an in-hull depthfinder is a lot easier than creating a new through-hull fitting.

Big brand or enthusiast brand

The largest manufacturer of tridata and depth finders is Airmar. While you may not have heard about it, if you own a tridata sensor or a plain depth finder, it is very likely made by Airmar. 

The big brands, Raymarine, Simrad, Garmin, and B&G, source sensors from Airmar and bundle them into their own packages with instrument displays and chartplotters. This is great for you as a sailor because it means finding replacements and getting service is easier.

Some enthusiast brands, such as NKE, offer their own range of high-accuracy sensors. These sensors often come with high-rate analogue signal output and require specialist processors for integration with the rest of your navigation data. The enthusiast sensors are typically single-purpose sensors, meaning you need more holes in your boat than with a tridata sensor. 

The NKE Log and Sounder interface, along with the electromagnetic NKE log.

For most cruisers, going with an Airmar sensor that connects via NMEA2000 is a reasonable and cost-effective choice.

The Orca Fleet

The Orca fleet consists of thousands of sailboats, and the fleet’s equipment is sampled regularly for remote diagnostics and support. As of January 2026, roughly 90% of the Orca fleet has a tridata sensor. The distribution by manufacturer is as follows:

Airmar is the undisputed leader in speed through water, depth, and temperature sensors.

Not surprisingly, Airmar is by far the largest manufacturer of sensors that report depth, speed through water or water temperature. 72% of these sensors report as an Airmar device either directly or via a gateway. The remaining is Garmin at 12% and a long tail of smaller manufacturers.

The DST800 is the most popular tridata sensor among Orca boaters.

As for models, the Airmar DST800 is the most popular model, covering more than 30% of all reported sensors, followed by DST810 and older DST models. 

If you are looking for a reliable and well-tested model, a modern Airmar sensor, ideally with calibration on the device head – like the DST810 – is a solid choice. If you are tired of paddlewheel maintenance and replacements, the Airmar UDST800 with an ultrasonic waterspeed sensor is a great option.

How to get the most out of your tridata sensor

Raw measurements create no value in themselves. You need a good way to visualize your sensor data to make better decisions at sea. Orca lets you create flexible instrument panels that show exactly what you need. For anchor and harbour approaches, a large and easily glanceable depth gauge is fantastic. 

A great example of polar instruments that let you compare your actuals against your polar targets.

While sailing, a wind rose and sailing performance metrics make it easier to hit your target angles and speeds. If you want inspiration for how to set up insightful instrument panels for sailing, visit the Orca Instrument Guide here.

Orca Core powers many of the advanced features in Orca.

If you want to get the most out of your boat’s sensors, then Orca Core is a great choice. It lets you view instruments on your phone and tablet, control your autopilot, and helps you make sense of your wind data with its built-in Sailing Processor.

Ready to upgrade? Order Orca Core today via the Orca Store and get free express shipping plus a 30‑day satisfaction guarantee.