A microfluidic system for performing fluid analysis is described having: (a) a submersible housing having a fluid analysis means and a power supply to provide power to said system; and (b) a substrate for receiving a fluid sample, having embedded therein a fluid sample inlet, a reagent inlet, a fluid sample outlet, and a mixing region in fluid communication with the fluid sample inlet, the reagent inlet, and the fluid sample outlet, and wherein the substrate includes a fluid drive means for moving the fluid sample through the substrate, and wherein the substrate interconnects with the housing. At least a portion of the fluid analysis means may be embedded in the substrate.