It's a cumulative song: add a new action for each verse.

SONS OF THE SEA

Sons of the sea,
Bobbing up and down like this.
Sailing the ocean,
Bobbing up and down like this.
Well you can build a ship my lad,
Bobbing up and down like this.
But you can't beat the boys in the bulldog ring,
Bobbing up and down like this.

Sons of the sea,
Hitching up your pants and bobbing up and down like this.
Sailing the ocean,
Hitching up your pants and bobbing up and down like this.
Well you can build a ship my lad,
Hitching up your pants and bobbing up and down like this.
But you can't beat the boys in the bulldog ring,
Hitching up your pants and bobbing up and down like this.


add in all 5:
Bobbing up and down like this.
Hitching up your pants and
Swabbing the decks and
Rowing the boats and
Climbing the ropes and

So the last verse would be sung:

CLIMBING the ropes and ROWING the boats and SWABBING the decks and HITCHING up your pants and BOBBING up and down like this.