I made some streams using vinyl floor tiles and brown coloured caulk. They came out looking pretty nice and I now have about 12' or streams that can be added to my existing vinyl tile rivers. These are really quick and easy to make and they look pretty nice.
There's more detailed info on my blog at: http://this28mmlife.blogspot.com/2021/06/row-row-row-your-boat.html
(https://1.bp.blogspot.com/-dIaJjJm4rZc/YL8KpzLt2vI/AAAAAAAAfHg/rrF5mpFnhlAFtphypPRzpHtpKzmoUmEUwCNcBGAsYHQ/s1021/Streams_1.jpg)
(https://1.bp.blogspot.com/-sQDNT5J5t_k/YL8KqPHkb2I/AAAAAAAAfHo/tsXvDIQHRwMoac-mR7q8fM6Km8xDvJVzQCNcBGAsYHQ/s1152/Streams_2.jpg)