You'll find this cache at a public boat launch at the end of Willow Lane in Portsmouth. All land surrounding the launch is private, but the launch itself is open to the public and stated so on a sign near the ramp.
Note there is no legal parking at the end of the ramp, but you should be okay for a few minutes to grab the cache. There is legal parking available on any of the streets that branch off Willow Lane.
You're looking for a camo bison tube. Hope you enjoy.