Complex sentence: While there are a several small islands in the lake, some of which are grouped near the mouth, the only significant island is Pulbah Island, which is located in the southern part of the lake south of Swansea.
Split into simpler sentences: While there are a several small islands in the lake. Some of which are grouped near the mouth, the only significant island is Pulbah Island, which is located in the southern part of the lake south of Swansea.