What is a must-have accessory for sun protection when visiting Hawaii?

UV-protected sunglasses are essential for sun protection in Hawaii, where the sun's rays can be particularly intense due to the state's tropical climate and geographical location. These sunglasses are designed to block harmful ultraviolet (UV) rays, which can cause serious damage to the eyes, including cataracts and other eye disorders. By wearing sunglasses that specifically offer UV protection, visitors can enjoy outdoor activities without risking their eye health.

The other options do not serve the primary purpose of sun protection as effectively. A hard hat is typically used for safety in construction sites and has no relevance to sun protection. A sun umbrella might provide some shade, but it is not as portable or effective as wearing sunglasses, especially when on the beach or engaging in active outdoor sports. A baseball bat is irrelevant in this context, as it serves no function regarding sun safety. Therefore, UV-protected sunglasses stand out as the most practical and effective accessory for protecting oneself from the sun while enjoying the beautiful scenery of Hawaii.