Blend together the blueberries, blackberries, and water until there are no chunks.

Strain out the berry juice from the skin and seeds using a mesh strainer. Use a spoon to press and move the mixture around to make sure you're getting all the liquid out.

Add the juice to a pot with the agar powder on medium heat.

Bring to a simmer for 30 seconds and remove from heat.

Spoon into molds and place in the fridge and let set, about 30 minutes.

Remove from molds. Store in a container in the fridge (if you don't eat them all right away!)