I would say "octopuses" personally. "Octopodes" is more etymologically correct but you run the risk of not being understood, and "octopi", while in common usage, is etymologically wrong and people who are aware of this might look down on you slightly.

"Octopuses" is both understandable and correct etymologically since "octopus" is a normal English word.

I sometimes say octopods.

Octopi is correct, in that it is an english language plural for octopus. It is not etymologically sound, certainly, as it's a latinate plural on a greek root.

So anyone telling you that any other form is wrong and insuating that 'octopi' is more correct is certainly asking to be mocked. But as we don't really do '-podes' in english, and "Octopusses" is a bit of a mouthful, I think we can accept any and all as more or less equally cromulent.

Tbh I'd understand it if you used all three forms. Octopuses is also etymologically incorrect, but the general public found it ok to use and it got generally accepted because people liked it. I don't see any reason for this to happen again with octopi, although now it might be more difficult.

Personally I'll use octopuses, just because I once confused octopi as a word for another species of the family octopodes belong to. Now I know it's a common plural, but it didn't sound like a plural to me back then.

I'd prefer to use octopodes, but I feel like this can too be confused with another species, and I don't want to sound all smart in saying it's actually a plural. Octopuses bypasses all that confusion, and probably everyone will understand that it's the plural of octopus, albeit some might have doubts whether it's the correct form or not.