how to tag floating pier/dock/swimming feature ?

This involves an attempt to resolve a Warning (on way 661080042), which then spread to an examination of adjacent way 658887377. The Warning (from JOSM) says 'barrier=yes is unspecific', and indeed it is.

A good image of the specific items in question can be seen at Fanning Spring State Park spring pool But note that another image suggests the arrangement has evolved over time. An overhead image (local property appraiser) suggests that the barrels may be the current configuration, in which case it is a barrier, but composed of floating barrels.

The items in question can be seen at the far edge of the spring pool. They are a multi-use floating man-made structure. The large vertical columns are steel pipes, embedded in the ground, which allow the surface structure to move higher and lower to track the current level of the water at the exit from the spring pool. If the river is in flood, it is possible for river water to backwash into the spring pool, which would also cause the structure to rise.

The intention of the structure is to allow visitors to walk across, swimmers to enter/exit the water, and to prevent boat/canoe traffic (arriving from the river) from entering the spring pool, while also giving the watercraft a place to tie up temporarily.

Structures similar to this exist along the river, at various boat launching points, to allow boats to tie up temporarily.

My question is how to map this ? It's not a dock=floating per the current page, and it doesn't look like a man_made=pier, type = floating. So what is best practice ?

An additional question concerns the waterway from the sprint to the river. Common term to describe this (at least in the US) is a 'Spring Run' or a 'Spring Branch. I see no similar terms available in the OSM vocabulary. Current usage seems to be water=stream. Could a better alternative be possible ?