Hola Nikita,

This is a great question and I can't resist a challenge. The sentence structure is confusing but if you break it into phrases it opens up possibilities. I would go for "gaze" or "watch" for mirar, especially when you see Tonina's steady gaze in the video; but it could be "see" meaning "to be mentally conscious of."  I think como is "like" meaning "in the same way as."

The intro. from Shui says that the lyrics are poetic and melancholy so we need to bear that in mind. It also seems to be a song of love and possibly loss. I think it translates like this:

"Remember that only the eagle crossing the blue world gazes like I gaze;

Remember that only the mermaids in the wide oceans sing like I sing."

Saludos. John