I had one of those expanding hoses. What it seems to be is surgical tubing inside hollow nylon webbing, with cheap looking plastic end fittings. Once filled by water pressure, it becomes relatively inflexible. It does not return to a compact, coiled shape, that's just how they package them. It's empty volume is less than that of a vinyl garden hose, but I don't know it's durable enough for boat or dock use.
I bought a 3 channel flat vinyl hose that winds up on a roll once. It, too, has cheap plastic fittings. But surprisingly, it has lasted a long time. I still use it from time to time, like when I haven't dug the hose reel out of the basement in the Spring. A bit limited in water volume compared to the regular round garden hose.
In the RV world, there are flat expandable hoses with fabric covering, and which can roll up on a reel. There are mixed reviews of representative samples on Amazon. One guy has used on his boat and loves it, others pan them due to leaks. Definitely would prefer one of them for storage space saving.