WIG craft have been used by border patrol troops as personnel transport over the water in North China for a long time. It is faster than patrol boats and can land the troops at riverbank with gentle slopes just like any boat.
It is basically a transport craft more suitable for calm water like lakes and rivers since it "flies" just a few meters above the water so that it stays within the ground effect zone, the lower the craft from water surface the more drag efficient due to higher air pressure below the wings.
For evacuation of wounded in open water, the design might have to be modified to make it a hybrid of WIG and conventional aircraft with stronger structure and larger wingspan so that it can fly higher above the waves. Normal WIG flies at 20 to 50 feet above the water. the abandoned huge Boeing Pelican WIG craft is an example of over ocean trans-continental capable high altitude WIG craft, but was too ambitious to be realized.