COROS HYDROP
COROS HYDROP
In essence. Castable underwater fishing sensor weighing just 10.6 g with 5 ATM water resistance. Measures depth, water temperature, color, and light intensity across each layer beneath the surface. Four sensors in a single body: barometer, accelerometer, temperature sensor, and RGB light sensor. Helps you pick the right lure, color, and the depth that fish are actually using. Pairs wirelessly via Bluetooth with COROS NOMAD or VERTIX 2/2S watches. Battery life of up to 13 days and USB-C charging in 1.5 hours.
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Product information
COROS HYDROP is a fishing sensor that brings a completely new layer of information to the water. It mounts on your line like a standard lure — cast it out, let it sink, and as you reel it back in it maps everything happening beneath the surface, from top to bottom.
Four sensors packed into one compact body — a barometer, accelerometer, temperature sensor and RGB light sensor — let HYDROP measure depth, water temperature at every layer, water colour and the amount of light reaching each depth. The moment you pull it out, all of that data appears as clear graphs directly on your COROS NOMAD or VERTIX 2/2S.
The workflow is deliberately simple. A short shake wakes the sensor up — cast it, let it reach the bottom, reel it in slowly and steadily. The whole scan takes a couple of minutes. When it's done, you know exactly where the temperature breaks are, how visibility changes with depth, and where the light falls off. That tells you which lure to use, what colour, and how deep to fish it.
The body is small and light — 10.6 g. USB-C charging takes around 1.5 hours and gets you approximately 13 days of regular use.
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Real subsurface data — temperature, depth, water colour and light intensity at every layer
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Four sensors in one body: barometer, accelerometer, temperature sensor and RGB light sensor
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Data displayed instantly on your COROS NOMAD or VERTIX 2/2S via Bluetooth
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Takes the guesswork out of lure selection — right colour, right depth, right retrieve speed
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5 ATM water resistance, operating temperature −20 °C to 50 °C
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Compact build, 10.6 g, up to 13 days of battery life
Product details
HYDROP works like a scout run before your first cast. As you retrieve it, it builds a vertical profile of the water column — layer by layer — giving you a complete picture of temperature breaks, clarity shifts and light penetration. By the time you pick up your rod, you're working from actual data rather than guesswork about what's happening below the surface.
Each data point matters for different reasons. Water temperature directly affects fish activity and metabolism — in summer most species hold in cooler, deeper water, in winter it tends to reverse. Water clarity and colour determine which lure colour has the best chance of being seen at all. And the light reading tells you whether fishing just under the surface makes sense, or whether you should be working the bottom.
HYDROP suits almost any fishing style — bank fishing, boat, kayak, fly fishing — and works equally well in fresh and salt water. It's particularly useful for mapping unfamiliar structure, locating productive spots and getting back to what worked last time. In tough conditions — murky water after rain, unknown reservoirs — it cuts through the uncertainty and gets you fishing smart from the first cast.
Every scan is automatically saved in the COROS app, geotagged to the exact spot with depth, temperature, water colour and light data attached. Over time you build a personal fishing log you can return to before any session. Pull it up, see what conditions looked like when you last caught fish there, and go in with a plan.
Frequently asked questions
Which watches work with HYDROP?
HYDROP pairs with COROS NOMAD, VERTIX 2 and VERTIX 2S.
How do I rig it?
Attach HYDROP through the eyelet at the end of the body, the same way you'd rig any lure. Add a clip sinker or drop-shot weight depending on how deep you want to scan — this helps it sink faster and reach the target depth. Let it sink to the bottom freely, then retrieve slowly and evenly.
How do I set it up for bank fishing?
Bank fishing works the same way — attach it through the eyelet like a standard lure. Because snagging on the bottom is more likely from shore, keep your casts shorter. A sliding float helps keep the line more vertical and reduces the chance of getting stuck. Let it sink freely, then retrieve slowly and steadily.
Can I use HYDROP in all fishing activity modes?
Yes. HYDROP is accessible within all fishing activity modes. Outside of them, you can reach it through the Toolbox menu — just select the HYDROP icon.
Is there a recommended scan duration?
Yes. One to one and a half minutes per cast is the sweet spot. A slow, smooth retrieve gives you the most accurate readings across all depths.
Does HYDROP need calibration?
No. HYDROP is factory-calibrated and requires no manual calibration.
How many scans can I do in a session?
There's no scan limit — it runs until the battery runs out. Expect around 13 days of use at a rate of 20 scans per day, each about 3 minutes long.
Can I review previous scans during an active session?
Yes. Past scans are accessible on the watch and in the app while a fishing activity is running. Go to the Toolbox menu or select a waypoint on the Explorer Map to pull up earlier readings.
How is HYDROP different from a fish finder?
HYDROP isn't a replacement for a fish finder — it does something different. It measures water column data that fish finders don't capture, and it works equally well from the bank or a boat.
Technical specifications
| Compatibility | COROS NOMAD, COROS VERTIX 2, COROS VERTIX 2S (via Bluetooth) |
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| Sensors | barometer, accelerometer, temperature sensor, RGB light sensor |
| Dimensions | 48.2 × 14.8 × 12.3 mm |
| Weight | 10.6 g |
| Sensor lens material | mineral glass |
| Body material | fibre-reinforced polymer |
| Water resistance | 5 ATM |
| Operating temperature | −20 °C to 50 °C |
| Storage temperature | −20 °C to 60 °C |
| Charging temperature | 0 °C to 45 °C |
| Battery capacity | 32 mAh |
| Battery life (regular use) | approximately 13 days |
| Continuous use | approximately 16 hours |
| Charging time | approximately 1.5 hours |
| Charging | USB‑C |
| Packaging | recycled paper |
| Manufacturer | COROS |
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