The following which can be found in the RYA Powerboat Course notes manual ( standard issue to all ISA / RYA Level 2 students is :
1- Light air ripples
2 - Light breeze small ripples
3 - Gentle breeze - somebreaking wave crests
4 - Moderate breeze fairly frequent white horses
5 - Fresh breeze many white horses some spray
6 - Strong breeze extensive white horses and spray
7 - Near gale very rough foam streaking down wind from wave crests
8 - Gale
9 - 12 Stay at home !
I also have another more detailed version in another book which I read recently ( but damned if I can remember where ! ) which in addition makes reference to the amount of canvas a smack can carry in the various wind strenghts !
Best wishes ,