This is a an open source robotic submarine built for the purpose of making underwater exploration accessible to everyone. Simply construct and plug in to your computer just like that you have your own little controllable robot to explore the sea! The OpenROV is 30cm long, 20cm wide, and 15cm tall. It weighs in at only 2.5kg and can go to depths of up to 100 meters. it takes just four ordinary C cell batteries which provide an hour and a half of run time. priced at $830.00 its pretty good as far as robots go if you have the tools and time to put it together. so whether you like discovering, exploring, just plain having fun or anything in between if you have the time, money and tools you should check it out
I highly recommend you check out the links below for more information. Also, this robot is open source, meaning you can examine the schematics and even make some custom mods.
web site: http://openrov.com/
infosource:http://www.kickstarter.com/projects/openrov/openrov-the-open-source-underwater-robot (kickstarter project finished but good video)