Tom this is not a bug, sure a horseman could probably swim across a river(can't be flowing to fast!), but that would require quite a bit of code, and some extra animations for the horseman swimming. Besides it would open up a whole buggy area of water travel, that Titi and Softcoder will probably not want to dive into just yet.
One last thing: Stop continuously asking for Titi, he hates it when you do that. If he doesn't respond here in a few days, send him a polite PM, inviting him to your topic.