It may be similar to a pike pole, however it commonly has a blunt tip, for pushing during undocking, with a hook for docking.
[1] It may be also used for pulling things out of water, such as debris or people, as well as for other fetching tasks and holding-off from other boats or landings.
Evidence of boat hooks has been found from ancient Rome and the painting Christ in the Storm on the Sea of Galilee, by Rembrandt van Rijn was painted in 1633 and clearly shows one in its familiar form.
It would have a brass hook- a non-rusting metal common on traditional boat fittings.
[2] Although the traditional boat hook is still available, various different materials, such as aluminium and even a rolled up polymer are now available.