You will spawn in the middle of the ocean next to bamboo and mushroom islands (bamboo jungle is located at coordinates 0 ~ 240). You can try starting island survival here or continue exploring the world. There are two useful structures near the spawn area: the shipwreck (-344 ~ -216) and the ocean ruins (-168 ~ 168).
How to use Bamboo and Mushroom Islands seed
Start the Singleplayer mode
Select ‘Create New World’
Then click on ‘More World Options…’
In the ‘Seed for the World generation’ field, enter -4810967597077705941