Job describes God alone as treading on the waves of the sea; Psalms likewise portray YHWH ruling the waters.
Job 9:8; Psalm 77:16-20; Psalm 107:23-30 provide important background.
The words ego eimi can ordinarily mean 'It is I,' so the divine-name argument should not rest on the phrase alone. The action and Old Testament imagery make the scene more significant.
Jesus performs an action associated with YHWH's sovereignty and accompanies it with language that participates in John's larger 'I am' pattern.
The disciples willingly receive Jesus into the boat.