Is the boardwalk a structure built under a permit, or is it exempt?
If a permitted structure, similar to a deck, then I would say that IRC Section R312.1.1 applies.
If it is not a permitted structure, then I would say that IRC Section R312.1.1 is advisable, but not required. The IRC, for means of egress, only requires that egress be extended to the required egress door. Once you hit the exit door, the means of egress has ended. This is often overlooked in my experience, as the IBC requires that egress be extended to the public way (see IBC Section 1028.5).
R311.1 Means of Egress
Dwellings shall be provided with a means of egress in accordance with this section. The means of egress shall provide a continuous and unobstructed path of vertical and horizontal egress travel from all portions of the dwelling to the required egress door without requiring travel through a garage. The required egress door shall open directly into a public way or to a yard or court that opens to a public way.