There are many factors to consider when selecting the proper current measuring equipment for your application. In general, you should know if you will be measuring current from an overhead structure or while wading. It also helps to know the approximate speed of the water to be measured.
Current meters are available in two styles.
The bucket wheel style looks very much like an anemometer which is used to measure air speed. Bucket wheel current meters are of stainless steel, brass, and bronze construction. Bucket wheel meters have a tail fin to keep the meter pointed directly into the current. This style of meter produces a signal which can be used with headphones, or a digital counter. There are several styles available which work on this principle.