I would question the added value. Stub ends do not provide any information about the purpose of the data. The highway tag overlaps with the water, which effectively produces a data error. ‘incline=0%’ is also an implied value.
Instead, I would use a leisure tag. leisure=bathing_place seems to be best suited. It is not advisable to use this on every ladder, but ideally to use it only in a very reduced way.
https://wiki.openstreetmap.org/wiki/Tag:leisure%3Dbathing_place