Pour water into a multi-functional pressure cooker (such as Instant Pot®) and insert the steamer basket. Place 2 ears of corn in the basket. Stack the other 2 ears on top, perpendicularly to the first 2. Close and lock the lid. Close the vent.
Select Meat/Stew setting and set timer for 2 minutes; allow 10 to 15 minutes for pressure to build.
Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove the lid.