Add the water and corn to the Instant Pot®. Lock the lid. Press the Manual or Pressure Cook button and adjust the time to 2 minutes. When the timer beeps, quick-release the pressure until the float valve drops. Unlock the lid.
Transfer the corn to a serving dish and let it cool enough to handle. Cut the kernels off the cobs.
In a large bowl, whisk together the lime juice and zest, oil, salt, and pepper. Toss in the corn, avocados, cucumber, and tomatoes
Cover and refrigerate until ready to serve. Serve chilled.