danieldegroot2
@wellmer Tag as seasonal
https://wiki.openstreetmap.org/wiki/Key:seasonal
i.e. seasonal=summer (it is present in summer, not in winter)

See also Associated features;
"Conditional restrictions could be used to give approximative opening dates. Ex: access:conditional=no @ Nov-Apr."
https://wiki.openstreetmap.org/wiki/Conditional_restrictions

Add a fixme if these values are estimated.
https://wiki.openstreetmap.org/wiki/Good_practice#Mark_estimations_with_fixme

Finally, you can remove the part of the note saying you don't know how to map it :-)

PS: The southern part of the footway not part of the bridge and located (outside the coastline) in the tidal range could be tagged
ford=yes
tidal=yes