This clip lock box (in a camo bag) is located within the Oystermouth Castle Grounds. These are free to access at any time, all year. Please don't try to get to the cache from the Quarry car park.
The easiest way to locate the cache is to head for one of the park benches in the grounds and then hone in on Ground Zero from there.
Please read the description which follows, if you would like to know about the "tunnel".

Trackables in the tb tunnel
For 5 years we have been working with the Hinderwell Pixie Clan to enable trackables to travel through their mining tunnel to England. Unfortunately, over the past few months, the tunnel has become increasingly unstable and as of August 2019 we have reluctantly had to discontinue our arrangement.
For anyone who is interested, photos of the tunnel travellers were often taken and can be seen in the Hinderwell Pixie Clan's Gallery
.
This means that trackables placed in this cache will no longer be transported to England. But trackables can still be dropped off and picked up here like any other cache.
Thanks to the Friends of Oystermouth Castle who gave permission to place the cache in the castle grounds.