In UWSN, during clustering, there may be occurrence of intra cluster collision. In order to overcome this issue, in this paper, we propose to design protocol to efficiently handle the intra-cluster collisions and to design sleep-wake up scheduling scheme for the data aggregation. In this case, the cluster head coordinates with its cluster members to transmit (append) their data packets with partially overlapping transmission times. After the CH finishes transmitting its packets to the courier nodes, it starts to receive incoming appended packets from its members. It then sends the packet to its parent CH towards the sink applying data fusion and sending the aggregated packet in TDMA period based on the receiver oriented sleep scheduling scheme. By simulation results, we show that the proposed technique minimizes collision and transmission delay.