In the tent, you can make the basic things you need to survive on a desert island. You will need a parachute cloth found on the shore to restore it, but then the tent will serve as shelter and a place to make water and ropes.

Water

Water is made in the Tent from Grass. To get it, tap on the Tent, then drag Grass to the center of the Tent. You can get Grass by cutting down shrubs in various locations.

Ropes 

Ropes are made from Grass and Flax. To get it, drag Grass to the center of the Tent. Flax can be grown in garden beds.