We've only seen them once and it was in a short scene where RJ knew it's content would be easily forgotten, because of the awesomeness around it:
I'm thinking it could very well be an Amayar Guide, that in death is saying goodbye to the very air itself.

From that little scene in WH, we know the Amayar follow the Water Way. It's a doctrine of peace, much like the Way of the Leaf, but given it's name -Water Way- perhaps more centered on the elements. We see in that one scene we have, that Timna (the Guide for the Sea Folk) even when she's just strolling lost in thought, she's very aware of the air around her;

Perhaps the Amayar Guides use what the elements, like water and wind, tell them, to Guide the Sea Folk. Like how Nynaeve can 'Listen to the Wind' and advises Rand on occasion on what she feels.

We also know through that same scene, that the Amayar consider their lives are lived in an Illusion. Again, as with the Water Way / Way of the Leaf similarities, this looks similar to how the Aiel consider their lives a Dream from wich they will wake on death.

I also think -considering my theory on Demandreds location with the Sea Folk- we might have a little more to learn on the Atha'an Miere and their relationship with the Amayar yet, considering it's the Amayar that through their Guides 'protect the Sea Folk from themselves'. (again, per Timna's PoV in WH).
Considering what we've read in KoD about how the mass suicide of the Amayar affected the Sea Folk Twelve and their Mistress of the Ships to such an extend, they thought it news that would 'make and anchor weep', I'm hoping this Memory#10 is a flashback that gives us readers more information about what impact the Amayar Mass suicide will have on the Sea Folk. Or that it's actually a surviving Amayar Guide, that waited with suicide with a message for the Sea Folk -a tiny speck of hope for the Sea Folk, so to speak- that will change their views at that point in the story.



*crosses fingers, thinking (and hoping) it's an Amayar Guide flashback*