The busy little Portage Bay located in Seattle’s Ship Canal is home to several boating clubs (Agua Verde, Seattle Yacht Club, and the Queen City Yacht Club), the NOAA Northwest Fisheries Science Center, and a quiet neighborhood of houseboats. Before the construction of the Ship Canal, transporting logs from Union Bay to Lake Union required a portage over the Montlake Isthmus, and Portage Bay earned its name by being the bay into which the logs were deposited.
There is a small beach on the northwest corner of West Montlake Park that has a small beach that provides the gentlest non-dock based launch point for Portage Bay. While there are usually a fair amount of small boats on the water, most of them are from one of the several previously mentioned boating clubs and are pretty harmless when given a wide berth. However, do be mindful of the vessels traveling through the ship canal, as many of them can be quite large.
Portage Bay, Union Bay, the Washington Arboretum, and Lake Washington can be accessed via the Montlake Cut to the east, and Lake Union can be reached by following the Ship Canal to the west.