Passage 4.35.9
γλαυκότατον μὲν οἶδα ὕδωρ θεασάμενος τὸ ἐν Θερμοπύλαις, οὔτι που πᾶν, ἀλλʼ ὅσον κάτεισιν ἐς τὴν κολυμβήθραν ἥντινα ὀνομάζουσιν οἱ ἐπιχώριοι Χύτρους γυναικείους· ξανθὸν δὲ ὕδωρ, οὐδέν τι ἀποδέον τὴν χρόαν αἵματος, Ἑβραίων ἡ γῆ παρέχεται πρὸς Ἰόππῃ πόλει· θαλάσσης μὲν ἐγγυτάτω τὸ ὕδωρ ἐστί, λόγον δὲ ἐς τὴν πηγὴν λέγουσιν οἱ ταύτῃ, Περσέα ἀνελόντα τὸ κῆτος, ᾧ τὴν παῖδα προκεῖσθαι τοῦ Κηφέως, ἐνταῦθα τὸ αἷμα ἀπονίψασθαι.
The bluest water I have seen is at Thermopylae—not all of it, of course, but only that which flows into the bathing pool known to the locals as the "Women's Pots." Near the city of Joppa, the land of the Hebrews yields water of a tawny color, not at all lacking the hue of blood. This water is very close to the sea, and the local inhabitants tell a story about the spring, that Perseus, after slaying the sea-monster to which Cepheus' daughter had been exposed, washed away the blood here.