1. Thru-hull transducers: These transducers are installed in the hull of the boat, making them the most permanent type of transducers. They work by emitting sonar waves through the hull, and then receiving the reflected echoes to create images of the fish and underwater structure. Thru-hull transducers are ideal for larger boats and provide better accuracy than other types.

2. In-hull transducers: These are similar to thru-hull transducers, but they are installed under the hull of the boat. They work by using a special adhesive to attach to the hull, with no protrusion into the water. In-hull transducers work well for fiberglass boats and offer good performance, but they are not as accurate as thru-hull transducers.

3. Transom-mount transducers: These are the most common type of fishfinder transducers. They are mounted on the transom of the boat, and they use a cone-shaped beam that emits sonar waves into the water and receives the echoes. Transom-mount transducers are easy to install and can work with various boat types.

4. Portable transducers: These are small and easy to transport, making them ideal for kayaks and small boats. Portable transducers are attached to a suction cup, and they can be easily attached and detached from the kayak or boat. They are battery-powered and can be placed in the water for real-time readings of the underwater landscape.

In summary, there are different types of fishfinder transducers available, each with its unique features and functions. The type of transducer you choose will depend on your boat type, budget, and fishing preference. Whether you choose a thru-hull, in-hull, transom-mount, or portable transducer, having a quality fishfinder will enhance your fishing experience.