It is a scyphozoan jellyfish of the order Semaeostomeae, due to the general body shape but mostly because of the marginal tentacles and elongated oral arms.
It is a member of the family Ulmaridae because the gastric cavity is divided in canals, as can be seen by transparency.
Subfamily Ulmarinae because tentacles arise from the margin and gonads are protrusive (the orange pleated tissue in the center).
The difference between the genera of this subfamily (Diplulmaris, Discomedusa, Floresca, Parumbrosa, Ulmaris, Undosa) are the number of sense organs (rhopalia) and the number of tentacles, besides some canal system organization.
As far as I can see the animal in the photo has 21 tentacles and 10 rhopalia (probably more of both). But the angle of the image does not allow me to see more.

I think it is a Diplulmaris antarctica, by the way from all valid species of the subfamily, this is the only one known from Antarctic waters. The species has 16 sense organs and 16-48 tentacles.
If you Google it, at least the first images are OK.