Croatian police have arrested a first officer following a collision between a catamaran and a sailing boat carrying Czech nationals on Sunday. The incident resulted in the sinking of the sailboat and the deaths of four Czech citizens. Authorities have not yet released the name of the arrested officer or details regarding the cause of the collision, but an investigation is underway. The collision occurred in the Adriatic Sea, a popular sailing destination. This incident marks a tragic loss for the Czech sailing community and has prompted scrutiny of maritime safety regulations in the region. Further details are expected as the investigation progresses and more information becomes available from Croatian authorities.