Place the baby potatoes, diced onion and corn in your Instant Pot (can skip this veggies step if you only want the crab). Sprinkle on 1 Tablespoon of the Old Bay Seasoning and add the water or beer.
Secure the lid on your IP and set to manual for 5 minutes. Quick release. Add the crab, remaining Old Bay and optional hot sauce to the Instant Pot. The crab should sit on top of the vegetables and not be submerged in the liquid. (if not adding veggies use a trivet on the bottom)
Secure the lid on your IP and set to manual for 5 minutes. Quick release and serve immediately.