I have two Garrity G-Tech floating lanterns. They have a special material in the handle, that is some kind of flotation device. The thing I don't get about it is you can unscrew a cap at the end of the handle and the flotation material comes right out.
Do they float? Yes.
I use them when I go fishing at night (I rarely do that.)
Are they rugged?
Yes and no; They have slightly more shock resistant than those Wal-Mart Ozark Trail Lanterns, and definitely more water resistant.
Would they survive a drop on concrete? I doubt it.
Are they good to have on a boat? Hell yeah, they float nicely, even with a 6 Volt Lantern battery inside.
They cast a very good beam, approx. half a mile just like advertised on Garrity's website.
http://www.garritylites.com/page102.html
I think they serve their purpose for what they are designed; fishing and boating.
I call my two that I have my "fisherman's lanterns".
I am surprised that they are not that popular here in Louisiana.
My wife bought both of mine on clearance at West Marine, they costed around $8.
Garrity is unfortunately a defunct company, so these lights will be increasingly harder to find.
Eveready's Utility lantern is also supposedly a floating lantern, but it's not water proof.
Those are the only floating lanterns I know of, and I hope I have been helpful.