Activate Mary Read and Anne Bonny by tapping it, causing you to draw a card and then discard an Island, Pirate or Vehicle card.
The discarded card is put on top of your library instead of into your graveyard due to Library of Leng.
Mary Read and Anne Bonny triggers, creating a tapped Treasure token.
When the Treasure enters the battlefield, Skyswimmer Koi triggers, causing you to draw a card and then discard an Island, Pirate or Vehicle card.
Repeat from step 2.
This clever loop starts by tapping Mary Read and Anne Bonny to draw and discard an eligible card like an Island, Pirate, or Vehicle. Library of Leng steps in to redirect that discarded card straight to the top of your library instead of the graveyard, allowing you to draw it right back over and over. Meanwhile, Mary Read and Anne Bonny rewards each of those specific discards by generating a tapped Treasure token. That arriving Treasure satisfies Skyswimmer Koi, whose artifact-entry trigger keeps the card-draw and discard engine churning endlessly without ever running out of fuel.