I was on hn when that happened last time. I felt like but could not convince someone to "buy" me an oil tanker for negative money, only for a short period but I could boast about "being an owner of an oil tanker once". Sigh. If only someone could help

It was the value of the contracts for delivery at a certain time and place (e.g. the "May 2020 WTI crude" contracts) that went negative, because there was no capacity to accept delivery.

Sure you could have received money by buying the (undeliverable) oil on a tanker, but then you would have been stuck paying the oil tanker lease cost (tens of thousands of USD/day) until capacity to take delivery became available, or until the tanker could be moved elsewhere with capacity.

oh no. making money was not the issue. i am living on the other side of the world so its not like i could take delivery even if i wanted to but the idea was that i could "buy" the contract and sell the same within minutes/hours as the price was in the negative itself.

i would've get a receipt in my name (for whatever brief period that would've been) and i would get to boast about that..... just harmless fun thing