Field Notes / October 2026
How to use PROBE to find the right depth
At a glance
| weight | 7 g / 0.25 oz |
| rating | 60 m / 200 ft |
| records | depth, temp, light, strikes |
| battery | 34+ hours |
Quick answer
Mount PROBE above your leader, fish normally, and let it log. Use the first few casts to read the water column (temperature and light by depth), then use the rest of the session to keep your lure in the band where fish are, and to confirm where they strike.
The problem
Underwater is a blind spot. You know roughly how deep the lake is and what the box says about your lure. You don't know the temperature down there, how deep your lure actually goes, or where the strike happened. PROBE was built to fill exactly those gaps.
01
Mount it
Thread the main line through the centre hole and lock PROBE in place with a float stopper on each side. Place it above the leader, a short distance from the lure. The body is hydrodynamic and centre-mounted, so it doesn't wobble or distract from the lure. PROBE connects over Bluetooth above the water only; underwater it stores everything and syncs the moment it surfaces.
02
Scout cast: read the column
Make your first casts long and let the lure sink or dive as deep as it will go. On the retrieve, PROBE records temperature and light level at every depth it passes. In the app, the cast graph shows:
- the temperature curve from top to bottom, including any thermocline (see What is a thermocline, and how do you find it?)
- the light level at each depth, which tells you how clear the water is today (see How water clarity changes the depth fish hunt at)
- how deep your lure actually ran, and how it reacted to reel stops and twitches
03
Pick the band
Match the column to your target species. Pike, perch and zander are cool-water fish; trout and salmon want colder water (see Preferred water temperatures for pike, zander, perch, trout and salmon). In summer, start at or just above the thermocline. In bright, clear conditions, go a little deeper; in dark water, go shallower.
04
Put the lure there, and keep it there
Most lures run at a different depth than the box says, because line diameter, line out and speed all change the result (see How deep does your lure really run? (It's not what the box says); see Braid vs mono: how your line changes lure depth). PROBE shows the real running depth of each cast. Adjust line, lure or retrieve until the graph sits in your band. For trolling, PROBE detects the session, plots route and speed, and shows lure depth in relation to boat speed, so you can see exactly which speed puts your lure at which depth.
Every cast logged. Every strike measured. No subscription.
See PROBE →05
Log the strike
When a fish hits, PROBE records the strike depth. Every cast is saved with GPS position and local weather, including the casts where nothing happened. That last part matters: empty casts tell you where fish weren't, which is half the answer (see What is strike depth, and why logging every cast (even the empty ones) catches more fish).
06
Build your own map
After a few trips, go back through the cast map and filter down to the spots where fish struck, then compare depth, temperature and weather. Patterns appear: the 4-metre edge that only produces when the water is under 12 °C, the bay that only works on overcast days. That is knowledge no chart sells you.
Field log /
A typical first session with PROBE, pike
| Scout casts | 3 |
| Found | Temperature drop at 6 m, light fades at 5 m |
| Lure adjusted | Switched to a deeper-diving crankbait, from 2.8 m to 4.9 m running depth |
| Result | 2 pike, both at 4.7–5.0 m |
The lure that had been fished all season ran 2 m above the fish. Five minutes of scouting changed that.
Field rule
Start every session with three scout casts. It takes two minutes and saves two hours.
FAQ
Frequently asked questions
Where do I mount PROBE?
On the main line above the leader, a short distance from the lure, locked in place with a float stopper on each side.
Does PROBE connect underwater?
No. It stores the data while it is underwater and syncs to the app over Bluetooth the moment it surfaces.
Do I need to watch the app while fishing?
No. Every cast is logged automatically, even with the phone in your pocket. Check it when you want.
Free app, no subscription, two-year warranty, ships within 24 hours.
Get PROBE →Sources