..... fabricating a magnetohydrodynamic propulsion system for OpenROV? The ROV wouldn't get tangled as much because of the lack of moving parts, it would be quieter in the water, and would likely cause less of a disturbance in a sandy or silty environment. It may only work in salt water, so it may take some development and engineering for freshwater.
More information at: http://www.evilmadscientist.com/2006/mhd-i-demonstrate-magnetohydrodynamic-propulsion-in-a-minute/