I think there might be a missing decimal point and that it's a 700 yard swim.
Generally the distances go: Ironman is 2.4 mile swim, 112 mile bike, 26.2 mile run; half-IM is 1.2 mile swim, 56 mile bike, 13.1 mile run; Olympic is 1.5km swim, 40 km bike, and 10 km run. There aren't standard distances for sprint triathlons but generally the swims are under 3/4 of mile, the bikes are under 20 miles, and the runs under 4 miles.
But to answer your original question, if you start swimming now, and keep at it, I bet you could very easily enter a sprint tri next season, not 3 years from now.