Echos of Levia Help Please?

Hi. I'm playing Echos of Levia and finding it rather addictive. As is always the case with these games, I've reached a sticking point and I'd be grateful for some help please? I've reached the marshes where you have to avoid the sulphur springs that suck you under. I seem to be going round in circles. The chiming noise which usually directs you to the next bit brings you to the no-go areas. I can hear frogs, but try as I might, I can't seem to get close enough to them. I'm assuming the frogs are a clue?

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