When the ocean becomes more acidic due to ocean acidification, it means the ocean is getting more acidic.
pH level measures how acidic or basic something is.
If something is more acidic, its pH level ↓ (goes down)
This happens because acidic substances have lower pH levels.
The normal pH of the ocean is around 8.1, which is slightly basic. As the ocean absorbs more CO2 from the atmosphere, it forms carbonic acid, making the ocean more acidic and its pH level ↓.