[pr_nik2]

One thing they struggled with was ballast. If you plan on carrying 100+ metric tons, what do you do once you're done? Suck up the nearest lake maybe and dump it back at base when you load your next cargo? Now this restricts your use cases. Not that many lakes people wanna part with in Africa...

[bolanyo]

100 metric tons of water isn't very much water. A medium sized swimming pool will have way more than 100 metric tons of water.

[mcv]

Can't you compress the helium and let in some normal air?

[perilunar]

Yes: https://en.wikipedia.org/wiki/Ballonet