The first spear strike must have hit and shredded something fleshy but by the time the sound reached him he had already taken another spear and hurled it. This time the Island silhouette has run back but the spear reached them.
Gong!
It hit a strong metal, a shield. Like before, by the time he heard the sound of impact he had grabbed another one and threw it, faster and stronger than before because he can no longer see their silhouette.
Gong!
But he can calculate how far the Island has run and shoot with accuracy to reach their new position!
Gong!
Gong!
Gong!
Silent!
Most Islands can't move fast at once, they drift and build momentum. Elias used that and predicted how far they had gone and barraged them with a spear. And each throw was targeted with the intent to kill.
On this journey, carrying a fragile object that may cause him difficulty if it breaks, He will not take any chances and be sloppy!