This was a swimsuit photo shoot designed to learn the tricks of daylight photography using a strobe to offset the sun.
One tool that I found indispensable was a light meter. Mine is the Sekonic L-358 Flash Master Light Meter. There are simpler meters available, but there was one feature that I found extremely useful. It has the ability to store two different ISO settings. If you only have one camera, you might not care, but I have two and was able to meter the light and know what to set as the light changed.