Penguins are my favourite animals!
My favourite species is New Zealand's Little Blue Penguin (which has close relatives in the White-flippered Penguin, which is still largely regarded as a colour-morph of the Little Blue, and also in Australia's Fairy Penguins, which look very similar but are much darker in colour), which are the world's smallest penguins. But you only tend to see the cold-climate varieties covered by virtual pets - and by most media in general.
But, of course, you can't keep a pet penguin, hence my aim to collect penguin virtual pets.
Yeah, I've heard that the Tamagotchi Ocean/Umi no Tamagotchi is pretty much the toughest Tamagotchi to raise, too...
Have you heard of Aquapalz? (Not to be confused with "Aquapets", which are something else entirely.)
It's a line of three aquatic virtual pets - a dolphin, a fish, and a jellyfish - with some interesting features. These pages have some information about them;
https://www.tamenagerie.com/odd25.html
https://tamagotchi.dreamwidth.org/14767.html
They sound quite interesting, and seem to have been well-received.