I just ordered a trolling lure that has a concave head. In the description it said it produced a bubble trail when trolled 5 - 10 knots. I never thought about it, but I guess the speed a turbulence causes oxygen to come out of solution, leaving a trail of bubble? Sorry for another simple question. I ask, because I am curious. I never thought about a lure causing oxygen to come out of solution. What else am I not aware of.... Don't answer that last question!