The correct option is C Fish
In the last lines of the first stanza, the speaker calls out to his 'brothers' (probably all of them are fishermen) and says that they should gather their nets and set sail on their catamarans to "capture the leaping wealth of the tide". In this context, we can deduce that "leaping wealth of the tide" refers to fishes and not water plants, fire or even waves. Option C is the best answer.