Alternatively, Thargoids with a sense of humour:Could there be a reason we're finding so much Tea (and Animal Meat - as opposed to what kind?!?) Are we assuming that the barnacles are going to be inert? Perhaps they are/were active and had a fondness for tea. Or animal meat. And attacked anything carrying them - hence the surfeit of wrecks containing these. (Maybe that's what MB's comments meant about the barnacles when he said you'll know when you see them..) Maybe we follow the wrecks to find the barnacles. Maybe we just carry lots of tea and animal meat and they'll find us?
It's been a while since I posted a wacky theory.. there was a grave danger of people starting to take me seriously.
1 - Intrepid explorer stumbles on Barnacle.
2 - Said explorer gets summarily assimilated.
3 - Body-count piles up.
4 - Thargoid necessitated to jettison waste/by-products, hence cannisters of liquids and solids.
5 - Vicious cycle continues