BESOM BRUSHES
The majority were found in a small compartment within the wreck on the orlop deck. Due to the number found, there was some confusion at first, as to their purpose. Why have so many 'twig brushes' on board a man-o-war? A further confusing factor was that each of them was covered/impregnated with tar or pitch in such a way as to indicate that they were originally stored on board in this condition? This would obviously have made them completely useless as a sweeping aid.
Click on any image to enlarge
Extensive research indicated that they were NOT in fact intended for sweeping up but used in a process known as 'BREAMING'. The following passage is an Admiralty instruction from mid eighteenth century: -
TO BREAM, CHAUFFER, FR. FROM BROOM.
TO BURN OFF THE FILTH, SUCH AS GRASS, OOZE, SHELLS, OR SEA WEED, FROM A SHIPS BOTTOM, THAT HAS GATHERED TO IT IN A VOYAGE, OR BY LYING LONG IN HARBOUR. THIS OPERATION IS PERFORMED BY HOLDING KINDLED FURZE, FAGGOTS, OR SUCH MATERIALS, TO THE BOTTOM, SO THAT THE FLAME INCORPORATING WITH THE PITCH, SULPHUR, &C. THAT HAD FORMERLEY COVERED IT, IMMEDIATELY LOOSENS AND THROWS OFF WHATEVER FILTH MAY HAVE ADHERED TO THE PLANKS.

AFTER THIS, THE BOTTOM IS COVERED ANEW WITH A COMPOSITION OF SULPHUR, TALLOW, &C., WHICH NOT ONLY MAKES IT SMOOTH AND SLIPPERY, SO AS TO DIVIDE THE FLUID MORE READILY, BUT ALSO POISENS AND DESTROYS THOSE WORMS WHICH EAT THROUGH THE PLANKS IN THE COURSE OF A VOYAGE. BREAMING MAY BE PERFORMED EITHER WHEN THE SHIP LIES AGROUND AFTER THE TIDE HAS EBBED FROM HER, OR BY DOCKING, OR BY CAREENING, WHICH SEE; AS ALSO COAT AND STUFF.

Note that the passage refers to "THE FLAME INCORPORATING WITH THE PITCH SULPHUR, &C." This ties in nicely with the pitch/tar found on the besoms when recovered from the wreck.
The average size is 700 mm long x 100 mm dia. at the tied end. I donated the majority to HMS Victory where they are now displayed on board Nelson's famous flagship in the Portsmouth Naval base.