First there's no shortcut to time on the water. Reading the reports and then comparing to experience is the best way to develop an understanding. If it feels a bit hairy on land it's for sure going to be rough on the water. When in doubt turn around and stay safe.
This is a wave's interval timed in seconds. The wave height is measured from the trough to the crest.
Every boat handles conditions differently and the reports are generally for the prevailing conditions, there can be odd ball waves etc. and just like on land weather reports are prone to be wrong and can change quickly so always need to keep that in mind.
For most boats most anything at a short interval 3-7 seconds is going to be choppy. Anything at a really long interval will be flat. Generally on the flattest days it's because you have 1-2ft waves at 10+ seconds or you have 4-6ft at a really long interval like 20 seconds with wind 5-10knts or less.
Here's a little snip of today. To me this is pretty calm seas it's not quite glass with 10kt winds that will put some texture on the water and kick up some small wind waves but that's some calm sees for Socal. Also having a W and S swell will cause a little washing machine effect but at the wave size and intervals it's still going to be pretty calm. When you see the intervals shorten and/or the peaks increase the more it does both, the more the water will give you a beating.