Blessing of the Devourer

The caster makes an arcana check, and, upon a high enough roll, is momentarily enveloped in bright green light. When the light dissipates, the caster's armor is covered in barnacles and seaweed, giving them +1 to AC. The caster's eyes are green, and their hair is with sea water. They have advantage on attacks against fire and lightning creatures. While the spell is in effect, they cannot die by drowning. Despite this, they cannot breathe underwater. If they spend enough time under water without air, or fail three death saves while in the water, they will become one of the Drowned. For every round the caster spend using the Blessing, they make a DC 14 Con save, and, upon a fail, lose 1d6 HP.