water bug

I've got some sort of "bug", maybe 3 mm long, several legs, clearish with blueish head that runs around on only one piece of LR. Runs as if he isn't in water at all (if that makes sense) fast.

I read the stickies and searched through this section. My biggest problem is I don't know what words to search with in google. It's not a worm or insect, but it looks more like an insect than a, um, anything else I can think of.

I can't get a picture of this little guy at all and I've only seen them twice (there's at least two). It's too small and by the time I get my camera out I can't find it again.

So I'm not looking for an ID (until I can get a pic) with this thread but looking for better words to put in google. Just trying to find the right tree to bark up, so to speak.

Thanks

 

see if you see it here.

Xtalreef