Bone Marine Armor (Womenswear) is crafted with Tailoring in Mabinogi (armor). This page lists everything needed to make it, checked against the game as it exists today. The interactive planner lives in the Tailoring Companion.
How to get the sewing pattern
The sewing pattern is rank 4 and survives 30 uses; every crafting attempt spends one use.
Shenon: Buy it from Shenon the sailor at the Port Ceann dock. (68,000 gold). No special requirements, just gold.
Myrddin: Buy it from Myrddin, the navigator aboard the Fishing Boat off the coast of Rano. (68,000 gold). Requires the Aspiring Sailor title equipped to board the Fishing Boat and reach him.
Sources that no longer exist: Production Gachapon (2012).
Materials
Expect about 6 attempts per finished item (17% average progress per attempt). Per-attempt materials are consumed on every attempt; finishing materials once per item.
Each attempt uses
3× Common Fabric — buy from NPC shops
4× Common Silk — buy from Seal Merchant (Mondays) for seals, or weave rank F
3× King Crab Shell — Fails a Braised King Crab cooking recipe by boiling King Crab without Celery.
Finishing (once per item)
1× Finest Finishing Thread — Buy directly from any general goods NPC shop.
1× Flying Fish Fin — Fail the Flying Fish Crepe recipe by cooking without egg or potato.