Above all, ensure that your snorkelling equipment is in good condition and fit for use. When in the water, avoid contact between your equipment and the local marine life or ruins. Be conscious of not stirring up sediment as this can harm the underwater ecosystem and compromise your visibility. Always snorkel or swim with at least one other person, never alone. It's also crucial to have someone watching over from the boat or shore. Be sure to familiarize yourself with any local regulations or restrictions regarding snorkelling in the areas you plan to visit.