loging radar/ sonar were can i by 1?

im trying by loging radar i dont not much about them other than there meny diffent kinds or radars i need one that detects logs from boat. its likes fish finder but i need someone tell me a good kind that work for logs like sed the are diffent ones i haveing trubell telling wich one will work for logs plz help maby tell me where i can buy one for my bissness. this find logs on bottem of lake to be pulled up and used for funicher hie end wood. plz help need to be able to see logs any one no anything about radars. its called swamp loging need loging radar for my boat. thank you and i want to see sopt were log is then go down right away and try pull if up with winch thank you could mabby tell me a good model that will work