Two brothers from Kenya were preparing their boats for a day of fishing on Lake Victoria. The younger and less experienced brother was confused when he saw a thick brown cloud near the middle of the lake. He wondered if something had caught on fire and asked his brother if they should check for any victims. Upon seeing the cloud, the older brother laughed and assured his brother that as long as they steered clear of the cloud, no one would be hurt. At the end of the day the younger brother laughed at his mistake and even appreciated the cloud as he ate his dinner. What was that mysterious cloud?