A flume tank is a model basin consisting of a large tank that the has water flowing through it. The velocity of the water can be changed to offer different current speeds or to model different vessel tow speeds. The tank is typically used to test small scale fishing gear for efficiency and economy. Some flume tanks over a moving floor that is designed somewhat like a conveyor belt this better models how a bottom trawl operates in the water column.
There are only a few large flume tanks in the world.
The Marine Institute's Flume Tank in Action: http://www.youtube.com/watch?v=M8O-Lw9K6Wo