Abstract We measured the angular scattering functions at 517 nm in different size fractions, including bulk and very small particles (VSP for diameters <0.2 μm), in a variety of waters ranging from coasts to open oceans and from surface to depths as deep as 3,000 m. The measurements revealed a strong covariation in backscattering between VSP and bulk particle populations. The fractional contribution by VSP decreases from 60% in clear oceanic water where bulk particle backscattering coefficient bbp is on the order of 0.001 m−1 to <2% in turbid coastal water where bbp ∼0.1 m−1. An empirical model is developed (r2 = 0.89) to estimate bbp for VSP from the bulk bbp, which can now be routinely obtained from satellite observations.