Ioun Stone Emerald Prism

Allows the use of slashing, blunt, ranged, or thrown weapons while underwater. It does not remove the Hindered penalty.

Hindered: When underwater, creatures not native to water (including player characters) are very slow to propel themselves. In melee combat, only characters with Free Movement may attack the first round. In addition, without magical aid anything requiring movement or a Move Action is not possible during the first round of combat.