Fish Finder Buyers Guide: How to Choose a Sounder

A fish finder, also called a sounder or a fish and depth finder, shows you what's under the boat: the depth, the shape of the bottom, structure, baitfish and fish. It's one of the best upgrades you can make to a fishing boat or kayak, because it helps you find fish rather than guess where they are.

This guide covers how a fish finder works, the main sonar types, fish finder GPS combos, and how to read a fish finder. Browse our range of fish finders and sounders.

How does a fish finder work?

A fish finder uses a transducer, mounted on or through the boat, to send sound waves down into the water. When those sound waves hit the bottom, fish or bait, they bounce back. The unit turns those echoes into a picture on the screen, updated constantly as you move.

Types of sonar

Most modern fish finders offer one or more of these, depending on the model and transducer:

• Traditional 2D sonar: the classic scrolling view showing depth, bottom and fish. Great for general fishing.
• CHIRP sonar: sends a sweep of frequencies rather than one, which generally gives clearer, more detailed returns and better separation of fish close together.
• Down imaging: a detailed, almost photo-like view of what's directly below the boat, useful for seeing structure clearly.
• Side imaging: scans out to each side of the boat, so you can search wide areas and find structure and schools quickly.
• Live sonar: shows fish and lures moving in real time. Garmin's LiveScope is one well-known example. It's the most advanced and generally the most expensive option.

What to look for in a fish finder

Screen size. A bigger screen is easier to read and lets you split the view between sonar and maps. Smaller units suit kayaks and small boats where space is tight.

GPS and maps. A fish finder GPS combo (often called a chartplotter combo) adds maps and lets you save your spots, mark fish and navigate back to them. For most boat anglers it's well worth having.

The transducer. The transducer decides which sonar types you can use. Check what's included in the box, and which mounting option suits your boat.

Networking. Some units link with other electronics, such as a compatible trolling motor. See our trolling motor buyers guide for more.

How to read a fish finder

Every brand displays things a little differently, but these basics apply to most traditional sonar screens:

• The bottom is shown as a solid band across the screen. A thick, bright band usually means a hard bottom such as rock or reef; a thinner, softer band usually means sand or mud.
• Fish often appear as arches on 2D sonar, because the boat passes over them. Their size and strength can give a rough idea of fish size.
• Baitfish usually show as clouds or clusters in the water column.
• Structure such as reef, weed and wrecks shows as shapes rising off the bottom.

The screen scrolls from right to left, so the newest information is on the right. Spend time learning what your local spots look like on screen, and it will quickly start to make sense.

Fish finder FAQs

Are fish finders worth it?

For most boat and kayak anglers, yes. Knowing the depth, bottom and where bait is holding saves a lot of time on the water.

Can I use a fish finder on a kayak?

Yes. There are compact units and kayak transducer mounts designed for this, and many run from a small battery.

Can I install a fish finder myself?

Many anglers do, following the manufacturer's instructions. If you're unsure about mounting the transducer or wiring, a marine professional can help.

Ready to choose? Browse our full range of fish finders and sounders.