Crests with glassy appearance , but do not break . Glassy looking foam , occasional white horses . Frequent white horses . Many white horses , some spray . Some large waves , extensive white foam crests , some spray .
Crests break into spin drift , blowing foam in well marked streaks .
Spray reduces visibility. Dense blowing foam , sea surface appears white . Heavy tumbling of sea , shock like . Poor visibility . Sea completely covered with long white patches of foam .