A center fed, three and a half turn hemispherical antenna on 3D printed Acrylonitrile butadiene styrene (ABS) material was designed as a floating antenna for coastal monitoring. Numerical modelling shows a return loss of -27dB at 772 MHz and a measured result return loss of -25dB at a resonant frequency of 765 MHz. The theoretical efficiency of the antenna in air and over water surface is 98.5% and 61%, respectively. The antenna has applications in wireless sensor networks (WSN) for coastal ocean monitoring.