You'll find you are going to need side imaging to find them. Once you are there, you'll need DI. A SI unit will have both. If you are going to buy just one, don't cheap out, you'll regret it.
2015 Seaark 1872 MV CC Etec-90
Helix 12 CHIRP SI, HB 1199, MinnKota Riptide ST80/i-pilot Link, Bob's Hydraulic
Bitter Gun Owner