Two instruments that measure similar optical properties of water were deployed from a common profiling device at the LEO-15 site during the 2001 HyCODE experiment. The AC-9 measures beam attenuation, c, using incandescent light sources, a colored filter wheel, and a receiver. It measures absorption, a, by including light that is scattered by particles over angles covering from about 0.75 to 41 degrees. The difference, c-a, can be computed to estimate the total scattering coefficient, b, over this angular range. The LISST-100 instrument measures beam attenuation using a laser. It measures scattering over 32 small angular ranges represented by ring detectors in the receiver optics. In contrast to the AC-9, the LISST-100 differs in two ways: first, its receiver aperture is much smaller at 0.05 degree thus rejecting scattered light more completely and producing a higher beam-c value. Second, the LISST-100 covers scattering measurements over the range 0.1-20 degrees, whereby it captures more of the forward scattering, but excludes the 20-41 degree range. The data obtained by these two instruments at the LEO-15 field site will be compared along with a discussion of the error sources. Variability in time and space of the attenuation and scattering coefficients will be related to the underlying particle composition, size distribution, and environmental forcing.