Walking under water and the city glitch
Make a Party game and get the Annihilator. Then, go to the second island's coastline and follow it until you reach the large parking lot. Jump down to the water and swim to the bottom side. Note: There are rocks on the side of the coastline. Swim to it and get on top of the rocks. You should be able to get on top of them before ending up going through them. Your character should now be on the bottom and won't be able to see until you walk down a short distance.