Combine shrimp shells, carrots, onion, celery, garlic, vinegar, salt, and pepper in a multi-functional pressure cooker (such as Instant Pot). Pour in water, then close and lock the lid. Select Manual according to manufacturer's instructions; set the timer for 60 minutes. Allow 10 minutes for pressure to build.
Release pressure using the natural-release method according to manufacturer's instructions, about 10 minutes. Release remaining pressure using the quick-release method, about 5 minutes. Unlock and remove the lid.
Pour liquid through a strainer and discard all solids.