We describe here the design, laboratory implementation and performance of an inexpensive yet reliable beam attenuation meter (transmissometer) for coastal ocean environmental monitoring. In its final operational form, this instrument is anticipated to be capable of measuring chlorophyll fluorescence as well. Given that the relevant parameters - water clarity, algal concentration - are indicators of coastal ecosystem health, low-cost optical instruments emerge as valuable tools for activities such as coastal engineering, fish-farming and water quality monitoring in recreation areas