This work investigates a joint power allocation and transmission scheduling algorithm for underwater acoustic (UWA) networks to improve the throughput by leveraging the low sound speed in water. We consider a round-based UWA system where transmission links are active concurrently to send multiple signal blocks during each round. To mitigate the interference, a quasi-interference alignment (IA) method is proposed where the interference signals are aligned as much as possible while a low level of collisions between useful and interference signals...