I don't see anything on the internet/brochures for Citroen C4 having the following:

Anti-Submarining Seat Pans

Anti-submarining pans are rigid seat-base structures that are designed to resist the tendency of the occupant's abdomen to slide under the lap portion of the seatbelt during a crash. Submarining can cause injury to internal organs and reduces the effectiveness of the seatbelt in retaining its occupant.

Can anyone confirm if this is the case?