What is the glue stuff you use to seal a glass shower panel to the tub?

I've got a frameless shower enclosure (I think that's what it is called) and the transparent glue/seal between the glass and the tub is peeling off. What is it? I'm guessing some kind of transparent silicone but my search-foo isn't working properly and I can't find it.

(I'm not talking about the hard plastic "sweep" that goes under the movable glass door. I'm talking about a very thin bead of transparent stuff along the boundary between glass and tub – as shown by the obligatory hand drawn red marks on the image below.)

P.S. If you've got any tips on how to replace this stuff properly I would be happy to read them in your answer!