From The Heroes of Might and Magic III wiki

This is a combination artifact.

Combination artifacts were introduced in the expansion Shadow of Death,
and are only available when it is installed.

Gives these advantages:

• No penalty when boarding / disembarking from a boat.
• Converts Movement points between land and sea.

To create this artifact you need Sea Captain's Hat and Necklace of Ocean Guidance.

You cannot purchase combination artifacts in Artifact Merchants. Cost is derived from sell price.

Basic Cost: 125000 gold