The correct answer is A) eddies below the bar. When steering a tow downstream around a sand bar, the operator should be cautious of eddies that can form below the bar. Eddies are circular currents that can pull the tow in unpredictable directions and make it difficult to maintain control. The swift current and changes in flow direction around the bar can create these eddies, posing a hazard that the operator must be alert to. The other answer choices are incorrect because: B) cross-currents pushing the tow away from the bar would not require special caution, C) cross-currents pushing the tow into the bar would be the opposite of the desired outcome, and D) swift current below the bar could contribute to the formation of eddies, but is not the primary hazard itself.