Each of the caches nearby named "TSPTOB" are part of the mystery cache "The Sunny Port Town Of Barnsley". You do not need to do the mystery cache to be able to find the indiviual caches, these can be done as standalones if you wish.
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Looking at your initiation scroll it looks like the captain wants you to run some surveillance on his enemies and check a nearby lootbox. The 'rope bridge' [use your imagination!] seems to be the highest vantage point. You're under strict instructions to only watch the enemies from afar [there's nothing in the enemy].
Good luck pirates!