Helena
There is a a large gravel parking area, a bit hard to see the entrance when arriving, but its there!
There are a few obvious trails from the parking lot to the river access. Upstream goes to a large rock you can sit on, or a nice curved section of gravel/sand bar. The downstream trail leads to another gravel bar with access to the swimming hole.
There is a tiny bit of sand here, mostly gravel and rocks. Between all beaches and rock out-croppings used for seating there is enough room for quite a few people, probably 20 or so comfortably. There is a conglomeration of large rocks in the middle between the 2 beach areas that can be used for seating/lounging and diving.
The current can be fast in the center of the pool , or close to the far bank. There's a section of fast-moving water feeding the swimming hole, depending on the time of year you go there may be more or less current. There are also shallow areas with no current.