Everyone Gets an Island: My Islands Are Invincible

In a different universe, everyone who reaches adulthood will be sent to a world that is surrounded by the ocean and become the owner of a small island! As long as one can protect your island, you will be able to reap endless benefits.
Immense strength! Longevity! Wealth! Status!
Peter activates a God Level Island System, getting many noob benefits right from the start and overtaking everyone else's starting point. There's no stopping him now!
He just plants a tree sapling and it grows into a dense forest overnight, bearing magical fruits!
He just rears a few fish and they transform into beautiful and extremely loyal mermaids!
Wait a minute...how did those whales become even larger than everyone else's islands?