This is done by using a Listen option on the shell, yielding the message: You listen to the ocean and hear whispers of great success for you and your team, in your next Fishing Trawler Game. and causes the player's character to perform an animation. The effect is then applied and the shell disappears. At the start of the next Fishing Trawler game all players affected by the boost get a chat notification (Your shimmering shell fills you with greater understanding of the sea. or Your teammate's shimmering shell fills you with a greater understanding of the ocean.).
The boosts cannot be stacked, and players can only have one shell in their inventory at a time.
The Shimmering shell is significantly rarer than its "solo" equivalent, the Glistening shell.