Place 1 cup of water (for 6 quart) or 1.5 cups water (for 8 quart) into the stainless steel inner pot of the Instant Pot. Place the trivet on top of the water, and place the fully frozen beef on the trivet.
Put the lid on, set the steam release handle to the 'sealing' position, and select pressure cook (or 'manual' for older models) for 5 minutes.
When the pressure cooking cycle is complete, carefully move the steam release handle to the 'venting' position (quick pressure release).
Using oven mitts, pull the trivet with the beef out of the pot. Pour the water out of the inner pot and return to the Instant Pot. Add the partially cooked ground beef back to the inner pot.
Set the Instant Pot to 'sautee', and cook for 2-3 minutes, breaking the meat up with a spatula, until it is cooked through with no pink remaining.
Add taco seasoning and water, and simmer for 1-2 more minutes, until sauce is thickened.
Using oven mitts, remove the inner pot from the Instant Pot to avoid it over-cooking.