Cool fins, anon! And is that a Heckler and Koch P11? You're so silly! You'll never nab a penguin with that little thing, and even if you did, with only five rounds, you won't be hunting for long. Plus, I've seen how you waddle around on the ice. A pepperbox pistol can't be very effective against bears. What you need is a truly amphibious rifle. With modern polymers, the issue of different cartridge sizes and bad ergonomics could be mitigated, and don't we already know how to deal with pressure issues in the barrel and receiver?
What's that? The Russian ones seem dubious? How about a gyrojet, then? Surely humans still like gyrojets?