I've got a paranah made by hummingbird.
I believe it's a 150 model single transducer, and seems to work great! Everytime it shows a school of fish, I time the boat distance and always get hits.
for the lakes around here it's pretty descent. Would recommend just getting something basic. Unless you like to spend money, and have the best of everything. I've only had this unit so I'm sure there are others that do work a little better. ( duel, triple transducer) anyways I really like how it is portable so I can transfer it from boat to boat, and I've ice fished with it.