Abstract: A fluid submersible sensing device is provided comprising a fluid-tight housing defining an internal chamber and including window structure; sensing structure provided in the internal chamber; light providing apparatus in the internal chamber emitting light capable of passing through the window structure so as to exit the housing; and a sample-providing structure coupled to the housing and located outside of the housing internal chamber comprising a passage through which a fluid flows. The passage may have a longitudinal axis substantially parallel with a flow path through the passage and a cross sectional area substantially transverse to the longitudinal axis. The light from the housing exits the housing, passes through the sample-providing structure including the passage and re-enters the housing toward the sensing structure.