I bought one of a Tpod SonarPhone about a month ago. Works pretty well from the bank, cast it out let it sit or crank it back in. You can also tow it behind a boat, they have some other portable models. I am enjoying my Tpod finding out things about small lakes and ponds.
The only draw back I have found so far is you can't scroll back.
http://sonarphone.mobi/