I've recently been working on my fletching skill for the shawl 2.0, and when I get bored farming stuff for the driftwood bows I hit air for the featherwood. It's faster to do the featherwood, except the mobs have a longer respawn, so if I've only time for one clear I'll hit up air instead of water. Per hour, you get slightly more bow combines out of water tho.
These drop alot during the spider ring near that rainbow click thing for the xegony event. It's a little bit hairy doing the event solo, but the part where all the lil spiders instant respawn...well...they can all drop the silk, so basically you farm the other mobs till your eyes bleed, then when you can't stand it anymore, you figure out how many cams and shafts you have, and then just kill those lil spiders while the big guy beats on you till you have enough silk. I got about 80 silks in 15 minutes.