Ultralight Dry-Bags?

I have no experience with this, but if you’re going to try this I would get the really heavy duty contractor bags available at paint stores and home improvement big box centers like Home Depot or Lowes. A pack liner might be in order as well,Gossamer Gear has them in inexpensive plastic and Sea to Summit has them in Ultra-Sil in 35,50,70 and 90 liter sizes on their web site. One of the larger ones could be a possibile alternative to the contractor bag. I’d also double(or triple) protect anything sensitive to moisture. Aloksacks from this website for smaller items and light weight dry bags for sleeping bags and clothing. There is a recent review of drybags here as well.
Tom

Never tried using them on the outside. I have swum a pack with a trash bag liner and everything individually bagged. The pack and harness got wet but the contents stayed dry.

Wet packs are heavier, but it was nice to wash some of the sweat out of the harness.

When I don’t expect to get my pack wet, I pack my goods in a decently durable plastic “trash compactor bag” type pack liner, like the ones sold here or over at Gossamergear.com.

Last year, I had an unexpected swim of the upper Yellowstone River, so I ended up putting the pack liner on the outside and using some shockcord to close it in twist-tie fashion.

By the time I got to the other side, my goods were dry.

However, the pack was a huge pain in the butt to swim with. Not having a shoulder harness to loop over one shoulder while you’re swimming would make fjord swimming laborious and makes river swimming difficult and risky.

I’d much prefer to have the pack harness available to me for swimming.