I got a handheld anemometer and like using it for measuring the wind speed as well as the air and water temperatures. The one thing to remember is that the reading will always be less than what is being recorded at a nearby weather station. While standing on the shore and with the anemometer held in the air it will only be 7 feet above the ground. While seated in the kayak it will only be a few feet above the water. These readings will be less than those placed at the standard height of 10 meters (33 feet). The wind speed is affected by the ground and any obstructions. This is similar to the affect of the shoreline affecting (and slowing) flow along a river.
A reading of 20 MPH at water level may actually equate to a wind of over 25 MPH at the normal height.
But, it is a good tool to be able to compare wind speed relative to other days. And the one I have with the ability to measure both air and water temperature is a handy tool also.