The Beaufort scale is used to rate sea conditions, with 0 for absolute flat calm and 12 for a hurricane with winds above 65 knots. When winds reach 22 knots, a Beaufort 6, it's virtually impossible to distinguish a blow from a whitecap, or to identify a seabird. For this reason the scientists go "off effort" until the winds are calmer. This was the heaviest sea we encountered during our cruise.