Crowdsourcing using low-cost measurement sensors is becoming a possible option for environmental sciences. This study describes the development and demonstration experiment of a prototype of the low-cost observation system for wind over the ocean. A validation experiment of the low-cost anemometer showed calibration is necessary to use the sensor for the field measurement. The sensor is next attached to the floating buoy and deployed to the harsh environment of the sea. The deployed system measured the wind over the coastal ocean in Sagami-bay for ten days consecutively. A good correlation for both measured wind speed and wind direction is found based on the comparison with results from a wind station at the coast. Issues related to the increase in the number of low-cost sensors are discussed.