Hi Mark, Yes, a hydrometer is by far the quickest and simplest way to measure salinity. It's a very simple device, essentially a glass tube, wider at one end, sealed at both ends, and with a weight permanently secured inside the wide end. When you place it in water, it floats vertically, with the weighted end down. Enclosed inside the narrow end is a numbered scale. The more dense the water (that is, the higher the salinity), the higher in the water the hydrometer floats. The salinity can be read directly from the numbered scale, at the air-water interface. Scientific supply houses carry them, usually about $15.00 to $20.00. Make sure you get a SALINITY hydrometer though (also called a salinimeter). Hydrometers are also made for many other purposes such as measuring sugar, acid, or alcohol concentrations, oil densities, etc. They all work the same way, but are calibrated for the specific purpose for which they were made. It is rather difficult to get a measurement by immersing the hydrometer directly in the ocean and trying to read it. You would want to have a glass container in which you could take a sample of the water, then float the hydrometer in the container. A glass laboratory graduated cylinder works very well. It can be a bit cumbersome carrying this glass apparatus in the field, and hydrometers are fairly fragile, but it will do the job if you want to carry it with you. Paul M.