Gear guide · Tech
Castable fish finder
How a castable fish finder like Deeper works, what it shows from the bank and which model fits you, with the maker’s own specs and videos.
How it works
- Charge it and pair it with the app. The sonar connects to your smartphone, the free Fish Deeper app shows the readings.
- Attach it to its own rod. Use a sturdy rod and strong line, not your fishing line with the hook. The maker shows the set-up in a short video below.
- Cast in a fan. From the bank the maker recommends casting at different angles to map drop-offs and find good spots.
- Reel in steadily. An even retrieve gives the sonar the most reliable data. Models with GPS draw a depth map from the bank as you go.
Shore routine from the maker’s help page.
- Good for
- Bank and pier fishing, bait boats, night fishing and, with most models, ice fishing and small boats.
- Not for
- Navigation. And it does not replace local knowledge: check access, private land and the rules of the water.
Deeper models compared
| Model | Casting range | Scanning depth | GPS, map from shore | Battery | Use |
|---|---|---|---|---|---|
| Deeper START | 50 m | 0.5 to 50 m | no | 6 h | Shore, night |
| Deeper PRO | 100 m | 0.5 to 80 m | no | 6 h | Shore, boat, night, ice |
| Deeper PRO+ | 100 m | 0.5 to 80 m | yes | 6 h | Shore, boat, night, ice |
| Deeper PRO+ 2 | 100 m | 0.15 to 100 m | yes | 9 h | Shore, boat, night, ice |
| Deeper CHIRP 2 | 120 m | 0.15 to 100 m | no | 15 h | Shore, boat, night, ice |
Maker specs from deepersonar.com, retrieved 29 October 2026. Shops sometimes use other names, such as CHIRP+ 2.
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Videos from the maker
Three short videos from the official YouTube channel Deeper Smart Sonar UK. The link opens YouTube, where Google’s privacy rules apply.
- Deeper PRO/CHIRP Series Quick Guide: How to Get Started Setup and first casts, 4:40 min
- What rod/line set-up would you recommend for casting? Rod, line and attachment, 1:44 min
- How do I know what I am looking at on the lakebed? Reading the lakebed, 1:45 min
No device: try the depth map first
Many lakes and coasts have officially surveyed depths. The Pescaday depth map shows drop-offs and the best bank spot, but no fish. A castable fish finder pays off when you want to see fish or your water has no map.
Quick answers
What is a castable fish finder?
A small floating sonar that you cast out on a rod. It sends depth, bottom structure and fish to your phone, so you can scan the water from the bank or a pier without a boat.
How does a castable fish finder work?
It sends sound pulses and times their echoes, like a boat fish finder. The readings go wirelessly to your phone, and models with GPS also map the depth as you reel in.
Which castable fish finder is the best?
It depends on how you fish. According to the maker, the START is the simple entry model, the PRO+ 2 adds GPS for depth maps from the bank, and the CHIRP 2 casts furthest and shows the most detail.
Can I use a castable fish finder everywhere?
That depends on the rules of the water. Check your permit or ask the club before you cast it the first time.