Oakum
Oakum is a preparation of tarred fibre used to seal gaps. Its main traditional applications were in shipbuilding, for caulking or packing the joints of timbers in wooden vessels and the deck planking of iron and steel ships; in plumbing, for sealing joints in cast iron pipe; and in log cabins for chinking. In ship caulking, it was forced between the seams using a hammer and a caulking iron, then sealed into place with hot pitch.
Zakynthos
The importance of this alliance for Athens was that it provided them with a source of tar. Tar is a more effective protector of ship planking than pitch (which is made from pine trees). The Athenian trireme fleet needed protection from rot, decay and the teredo, so this new source of tar was valuable to them. The tar was dredged up from the bottom of a lake (now known as Lake Keri) using leafy myrtle branches tied to the ends of poles. It was then collected in pots and could be carried to the beach and swabbed directly onto ship hulls. Alternatively, the tar could be shipped to the Athenian naval yard at the Piraeus for storage.