if you hang in the 10 to 20 watt region no circulation necessary. It would take a long time to rise the water temp to any significant level. Never measured it or the rise but usually the volume is enough to be a good enough heatsink for the tip of a fiber. I would also like to add, you dont want the focal point right on the tip just keep it slightly out of focus so that it couples but not cooks it.
Sorry the go pro was the only camera i had available this morning, ive gotta run. But here it is, of course I made a special housing i could put on a post and stand to get the alignment but you get the idea.