Yes I know there are boat rezzing zones, almost all on islands or other public places, few close to residential areas. In small streams the rezz zones are none, and small streams are not connected to the main water and stay at different altitude. Where my camper is (placid) we have a nice stream with some piers where it is possible to sit, but nothing about boating nor swimming, nor fishing.
Of course you could always teleport to a location where you can find them, but, let me see that the user experience will not be the best of all.
There is a lot of unexpressed potential in those areas that could be exploited with minimal effort.