Econea®, or 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile, is a new type of environmentally friendly anti-fouling compound used in the immersed coatings of commercial sea going vessels. This paper reports the development of a new analytical method to directly detect the active biocide Econea® in an artificial sea water matrix using liquid chromatography mass spectrometry. The developed method is both rapid and sensitive, with a limit of detection of 0.05 μg/L and a limit of quantitation of 0.17 μg/L in artificial seawater. The subsequent developed method was then applied to investigate the biocide’s release from a commercially available Econea® containing paint immersed in artificial sea water over a 45-day period. It was found that the average release rate of Econea® from this paint was 4.3 ± 0.6 μg cm−2 d−1.