And such as are in the sea,— As the inhabitants of the watery element are necessarily mute, we are not to understand by this, that they seemed to grow vocal in the praises of Christ upon this occasion; but rather that heaven, earth, and sea are used to signify, that all nature in its different ways concurred in the acclamation; that is, that the whole constitution of it contributed to furnish out matter of praise; just as inanimate as well as rational creatures are called upon to praise God in several of the Psalms, especially in Psalms 148.
Related Commentaries of Revelation 5:13
Revelation 5:13
13 And every creature which is in heaven, and on the earth, and under the earth, and such as are in the sea, and all that are in them, heard I saying, Blessing, and honour, and glory, and power, be unto him that sitteth upon the throne, and unto the Lamb for ever and ever.