After your first arrival on the Golden Apple Archipelago in Genshin Impact, you will be able to explore the area and start a new task. As long as the three devices are activated and the fog is removed, you will be able to do the main cannon, get ready, shoot! part of the Midsummer Island Adventure event.
This includes bypassing maps of Hilichurl fighting groups. To earn rewards, you will have to complete certain challenges, including collecting Shiny Flotsam.
Flotsam can be earned by sailing to the Hilichurl plateaus and evacuating the enemies you find there. These platforms will be marked on your map with small Hilichurl icons.
When you arrive, you will find many enemies on both small and large platforms. Smaller platforms can destroy your ship, but you will have to leave the ship and jump on larger platforms to eliminate the enemies that are there.
By completely clearing the platforms, you get 200 Shiny Flotsam, which will count towards your daily calls for action. You won’t get 200 shiny floats until the last enemy is dead, so clear them all.
You should also be sure to destroy as many platforms, crates or barricades as possible, as this will require different challenges, making it more efficient to work on everything at once.