Collect 4 to 10 logs. Lay them gently into the shallow water near shore that is deep enough for the logs to float. Choose equal sized logs because they fit better (be careful not to lay the logs into a rough sea because they might float away!).
Collect 6 poles that are longer than the logs. At one end of the bunched up logs, put a pole under the logs crosswise with a matching pole above. Repeat the process, with the remaining poles, space them to the opposite end of the raft. Gently ensure that there are no big gaps between the logs or you may lose your valuable possessions while at sea.
Tie the ends of the poles together at each end to clamp the logs tightly. Scan the island for strong vines and rope like plants which may provide you with strong fastenings.
Scan the area. Planks, driftwood and tree bark can be laid on the top sides of the cross poles to create an elevated platform. Bark works well and floats easily but split driftwood with the smooth, round side up looks more natural furthermore, it lasts longer in harsh weather conditions
Done, In addition to this design, you could add a sail if you can locate any washed up sacking or old ship sails. After scanning your location, you might also find a large palm leaf which may work just as well.