Halakhah for Chullin 177:35

1. The color of the body of the Hillazon resembles the color of the sea as the Rabbis in Tractate Menachot (44A) taught that the color of the Hillazon resembles the color of the sea. Rashi explains that the Hillazon emerges from the sea and the Techelet resembles the sea, that is to say that the sea it is found in and that it emerges from is the cause of its color.