In test game mode you can press F11
Down at the bottom of the screen are things you can shut of.
Or the water and the terrain can be shut off or on thru scripting. Check out the script board of this site or do a search, to find them. I have not tried it yet.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit