I have cruised from Hawaii to Vancouver and while the temperature was not the greatest, especially the closer we got to Vancouver, the seas were little or no problem. This was in May and usually the seas are relatively good during that time of year.
That does not mean that on any given cruise you won't encounter some rough water but there are rarely cruises in which the entire voyage is continually rough. Ships plot their courses to "try" and avoid rough seas. Sometimes they can't be but they try to minimize it.
Also, one person's light chop is another person's tidal wave.
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"There is a great difference between being well traveled and just having been to many places." ~Me