Once upon a time, a devilish imp inhabited a dark grotto near Patonga, until in early 2020 a Great Flood and Pestilence drove it away and peace returned to the village. But rumours have spread that another evil spirit, recently evicted from his Cave of Power by Muggledom raiders, has now taken up residence in the grotto.
This spirit's greatest power comes from darkness and GZ is totally dark, so you'll need plenty of illumination to reveal him in your search and hold him at bay while signing the logbook. On no account let your light go out, or you may not live to log your find online. The logbook can be accessed from under his robe; please don't try to remove him from his den as he's firmly attached to it. A pencil is included.
Depending on recent rainfall and tides, you may need to wade to reach his abode. I recommend bare feet (of course!) but if you must wear shoes, make sure they're water-tolerant. It's best not to attempt this cache during heavy rain or for a few days afterwards, as the normal trickle of water can turn into a raging torrent and more than just your feet will get wet.
The background image may help in your quest. The cache is anchored to the ceiling and by necessity is fairly high. I'm 175cm and can easily reach the logbook's container without stretching, but someone significantly shorter may need to bring something to stand on. There are some loose rocks in and around the grotto that could be used at a pinch.
Congratulations to P3sKy_Geomonkey, the first to confront the grotto's resident and live to tell the tale!