Unfortunately it's all to do with the wind versus the tide - there's no real calmer areas, unless you can find a nice sheltered cove somewhere.
I was out diving in the Solent (from Lymington) on sunday and it was lovely when we set off, but as we cleared the Needles the wind got up and there was a Sea State of about 4/5 which wan't too pleasant for most of the divers in the boat! I was one of only three not to feed the fishies!
There's weather out there - must be time to RIB!
(Or dive, or ref rugby, or.......)