3 His face was rugged, and his hoary head

rugged > hairy

4 Dropped with brackish dew; his three-forked pike

Dropped > Sprinkled three-forked pike > [trident]

5 He sternly shook, and therewith fierce did strike

sternly > fiercely; grimly therewith > with it

6 The raging billows, that on every side

that > [so that]

7 They trembling stood, and made a long broad dike, 8 That his swift charet might have passage wide,

That > [So that] charet > chariot