Then, as a fisherman might observe a fish in the water, Death observed the Devas in the Rik, Yagus, and Sâman-(sacrifices). And the Devas seeing this, rose from the Rik, Yagus, and Sâman-sacrifices, and entered the Svara, i.e. the Om (they meditated on the Om).

In plain words: Death still saw the gods inside their rituals, the way a fisherman spots a fish in clear water. When the gods noticed this, they left the rituals behind and went into Om, the sacred sound, by meditating on it.