Please correct me if I do any language mistake because I'm from Poland.
Sometimes when you are on Journey you get hurted and you need to heal yourself. Leeches take a lot of space in inventory.
The solution is Glass jar or normal Jar of leeches:
It should works like a seedbag but now you store leeches not seeds.
You create it from 1 L water and Jar of course.
It can be usable in fishing too!