As the next guy said, it's the period of the waves. I don't know about Lake
Michigan, but if it's anything like Lake Ontario, the waves can be stranger
than on the ocean. I was out a couple of nights ago (14 ft Lund) in 2 ft
wave, which are usually meaningless. But on this particular night, something
about the rhythm of the waves was downright spooky. Ended up anchored behind
a jetty, fishing for bluegills, rather than trolling for bigger fish. :-(

"Dionysus Feldman" wrote in message
...
Does anyone have any advice for facing 3+ foot waves in a 24-foot (Sea
Ray 240 SRV -- planing -- ~5000 lb displacement) boat?

How do I know the difference between the jitters and being stupid?

(We want to go across Lake Michigan to Chicago this weekend, and the
weather might be rough.)