As May 5 faded into darkness, "Tay" counted seven U-boats surfaced in the convoy's path; but ONS 5 was entering the fog formed where the warm Gulf Stream meets the cold Labrador Current off the Grand Banks of Newfoundland. Visibility dropped to by 2202 and to by 0100. British centimetric radar enabled the escorts to see while the U-boats could not. Many of the U-boats involved never returned to base to file their reports; so historians still struggle to correlate individual reports of the dozens of ships interacting briefly in no fewer than 24 attempted attacks on the night of 5/6 May.