Passage 2.37.6
καὶ τόδε ἤκουσα ἄλλο· τὸ ὕδωρ τῆς λίμνης ὡς ἰδόντα εἰκάσαι γαληνόν ἐστι καὶ ἠρεμαῖον, παρεχόμενον δὲ ὄψιν τοιαύτην διανήχεσθαι τολμήσαντα πάντα τινὰ καθέλκειν πέφυκε καὶ ἐς βυθὸν ὑπολαβὸν ἀπήνεγκε. περίοδος δὲ τῆς λίμνης ἐστὶν οὐ πολλή, ἀλλὰ ὅσον τε σταδίου τρίτον· ἐπὶ δὲ τοῖς χείλεσιν αὐτῆς πόα καὶ σχοῖνοι πεφύκασι. τὰ δὲ ἐς αὐτὴν Διονύσῳ δρώμενα ἐν νυκτὶ κατὰ ἔτος ἕκαστον οὐχ ὅσιον ἐς ἅπαντας ἦν μοι γράψαι.
I also heard this other thing: the water of the lake, to one who sees it, appears calm and gentle; but despite this appearance, it is by nature such that anyone daring to swim across is dragged down—it seizes him, carries him below to the depths, and does not release him again. The circuit of the lake is small, about one-third of a stade, and along its banks grass and reeds grow. Concerning the rites performed yearly at night here in honor of Dionysus, it would not have been proper for me to write openly for everyone.