A spectroscopic detector suitable for detecting oil spills in an aquatic environment includes a buoyant container having an optical window; an optical energy generator mounted in the container for directing an optical energy beam through the window; an optical detector for generating an output signal in response to detecting a second optical energy beam received in the container through the window; and a beam splitter for directing the second optical energy beam to the optical detector. The generation of the optical energy beam and operation of the optical detector may be time gated to reduce thermal noise and isolate the sampled optical energy from background light. The optical energy beam preferably has UV components which inhibits the formation of biological organisms on the optical window.