Measuring lake depth (Fish FInder)

Hi, this topic seems to have been discussed many times in the past but I would like to re-open this discussion to see if there are any new cheaper options. My idea was to attach the transducer and converter to a bobber on my fishing line and read the lake depth at intervals as I reel it in. I was hoping to store this data on a usb and then upload it to my laptop. I am new to arduino's and I would like some guidance.

I would suggest the obvious qustion back is 'cheaper than what' ?

Look on eBay for some cheap fish finders. Some have Bluetooth.

I have this one and it works pretty well (up to 100 m depth), but would have to be reverse engineered for Arduino.

srnet:
I would suggest the obvious qustion back is 'cheaper than what' ?

Cheaper then echo sounder transducers were in 2012, when the other posts were made.

jremington:
Look on eBay for some cheap fish finders. Some have Bluetooth.

I have this one and it works pretty well (up to 100 m depth), but would have to be reverse engineered for Arduino.

How difficult would this be for a beginner to electronics?

If you mean to reverse engineer, very difficult to impossible for a beginner.