Passage 8.22.9
φασὶ δὲ ἕπεσθαι θηρευτὴν ἄνδρα ἐλάφῳ φευγούσῃ, καὶ τὴν μὲν ἐς τὸ τέλμα ἵεσθαι, τὸν δὲ ἄνδρα τὸν θηρευτὴν ἐπακολουθοῦντα ὑπὸ τοῦ θυμοῦ κατόπιν τῆς ἐλάφου νήχεσθαι· καὶ οὕτω τὸ βάραθρον τήν τε ἔλαφον καὶ ἐπʼ αὐτῇ τὸν ἄνδρα ὑπεδέξατο. τούτοις δὲ τοῦ ποταμοῦ τὸ ὕδωρ ἐπακολουθῆσαί φασιν, ὥστε ἐς ἡμέραν Στυμφαλίοις ἐξήραντο ἅπαν τοῦ πεδίου τὸ λιμνάζον· καὶ ἀπὸ τούτου τῇ Ἀρτέμιδι τὴν ἑορτὴν φιλοτιμίᾳ πλέονι ἄγουσι.
They say that once a hunter was pursuing a fleeing deer. The deer rushed into the marsh, and the hunter, driven by his passion, swam after it; thus, the chasm swallowed both the deer and the man chasing it. It is said that the water from the river followed after them, so that in a single day the marshy water covering all the plain of Stymphalus was drained away completely. Because of this event, the people now celebrate the festival of Artemis with even greater eagerness.