Complex sentence: In order to cope with the pressure, many fish are rather small, usually not exceeding 25 cm in length, and scientists have discovered that the deeper these creatures live, the more gelatinous its flesh and the more minimal its skeletal structure.
Split into simpler sentences: In order to cope with the pressure, many fish are rather small, usually not exceeding 25 cm in length. Also, scientists have discovered that the deeper these creatures live, the more gelatinous its flesh and the more minimal its skeletal structure.