Some people think that is found only on the Desert island, but it can also be found at the arches, only not a full cactus only a single block. It cannot be eaten and has no use in crafting. However, it has a property that only a few items have, and that is a weld surface, allowing it to stick onto any surface and anything to stick onto it, including ships. It cannot be planted. It should be noted that the cactus does not deal damage to the player when touched.
Since cactus has a weld surface, it is possible to build your own structures with it. A person with a very creative mind can also use it to modify vehicles such as carts, siege towers, ships, and others. Cactus can be used to create "stepping stones" to reach higher surfaces, as it can stick to walls. Cactus can be used to waterproof ships, and a way to escape an island. Cactus is also flammable, so it is not recommended to use it to modify large ships, as griefers will target large structures and burn them down, wasting hard work.