Brihaspati is the guru and priest of the gods — the deity of wisdom and learning. He stands first among all priests. Skanda — also known as Kartikeya — is the commander of the celestial armies. Wisdom and valour, both divine.
And among bodies of water, the ocean. The ocean's vastness, its depth, its capacity to receive all rivers without overflowing — these qualities mirror the divine. That which is largest, which absorbs all streams into itself — that is the vibhuti.