To be "short" you can sell borrowed equities, sell calls that you write, or buy put options. Buying put options will cap your risk at the option price (I think underwater just meant "lost lots of money" - more likely to go out of bounds with the first two kinds of short positions)

Sorry, but no.

Those three are all 'bearish' strategies, but "going short" is selling something you don't have. Buying put options isn't short selling, although both are anticipating a decrease in the value of something.

Underwater is the term for a contract or asset that is worth less than its notional value.

https://www.investopedia.com/articles/trading/092613/differe...

https://www.investopedia.com/terms/u/underwater.asp

Thanks for the clarification. I used "short" in quotes as that was the article terminology.

If the asset he has bought is now cheaper, then yes he is "underwater" (i.e he has lost money on a mark-to-market basis - if he was to close out he would crystallize a loss)