You need to be on an irradiated planet, but those can have several names, not just "irradiated". They include:

Irradiated
Radioactive
Contaminated
Nuclear
Isotopic
Decaying Nuclear
Gamma-Intensive
High Radio Source
Supercritical
High Energy

Note that not every fish on an irradiated planet is an irradiated fish - you can catch common fish as well, for example. So 2 catching 2 uncommon fish on an irradiated planet doesn't count, they need to both be uncommon AND irradiated.

You cannot drive the skiff.

Yes, you have to be on a radioactive planet to catch a radioactive fish.

While you are standing on your skiff, further attempts to summon it will cause it to drift slowly to the position indicated by the green hologram. If you are not standing on your skiff it will instead vanish then immediately reappear at the designated location.

Thanks very much!

The skiff seems to be a solution looking for a problem. If it was not for the cold storage, it would be completely useless.

Other than the cold storage extra inventory, a ship with Aquajets, especially a ship with hover (and Aquajets) is a better fishing skiff than the Fishing Skiff.

Note: The Fishing Skiff DOES have one TINY environment proof spot, in the center front of the transparent part of the deck. If you are patient enough to tweak your stance onto it, that can be useful for fishing rares, legendaries, and enourmous types, which typically require a lot of casts. Note that you will slide a bit when water washes over the deck, so it can be hard to keep ON "The Spot" in storms.