It was in Lake Calhoun in Minneapolis, which is about 300 acres and a maximum depth of 80 feet. I'm not sure how deep it was at the point my buddy went over, but judging by
this map, it was probably about 60' where it was lost. The boat drifted pretty quickly to the northern shore of the lake (where we tied it to a buoy to prevent it from drifting into a rock retaining wall, as it was too windy and too late in the day to right it then). If the sail didn't get dragged to bottom of the lake immediately, it probably drifted in that direction, too, where it may be as shallow as 30'-40'.
Funny enough, I posted a "Lost & Found" on craigslist last night in case any craigslister who was walking around the lake happened to spot it on a beach, and I got a reply from someone who is going on a recreational dive on Saturday who said he'd keep an eye out for it. I've no idea who he is, but I wish him the best in finding my jib!
If we don't find it, we might go for a solid color jib in turquoise or something else complementary!