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From Pathfinder Lost Omens High Seas, which isn't enabled.

Coral Aspect

ITEM 4
Price 80 gp
Usage worn mask
Bulk L

Made of petrified wood, this mask evokes the form of a coral reef. When you wear it, you gain a +1 item bonus to Athletics checks to Swim, and any armor you're wearing gains the aquadynamic trait.

Activate—Cohabitate (concentrate, manipulate, polymorph)
Frequency once per day

Effect For 1 minute, your body becomes a mobile coral reef, letting much smaller creatures pass through or shelter in it. Creatures at least one size category smaller than you can share your space. Allies that share your space gain a +2 circumstance bonus to their AC, and you gain resistance 5 to any damage caused by a creature sharing the same space as you.
Pathfinder Lost Omens High SeasORC