I've been distracted by other research but now I've got some time to make some progress. I'm such a noob that this stuff is like learning a new language. I've been reading a few books on sketching to get it going.
Equipment list:
-Airmar Transducer: off the shelf, basically a piezo-electric sensor that pings and receives. Sound travels ~1560 m/s through water depending on temperature, 2 way travel time between the ping and reception of the ping will then be used to calculate depth in meters. I plan on using an adaptation of the "Ping" sketch to operate the depth sounder.
-Arduino: Controlling and computing
-EM406 GPS: Location reference
-SD Card Shield: Data logging
The hardest part is getting the GPS to log the location and the Transducer to log the depth simultaneously in one file on the SD card.
My Sparkfun package arrives this weekend with the missing prototyping components. I'll be sure to post if I get things pinging.
Any tips/suggestions are always a appreciated. I did get a Arduino Mega as suggested btw.