Yes, there are risks associated with dogs drinking lake or ocean water. Lake water may contain harmful bacteria or parasites that can lead to gastrointestinal issues, while ocean water's salt content can cause dehydration and salt poisoning. To avoid this, always provide fresh, clean water for your dog and encourage them to drink it regularly, especially before boarding the boat. Keep a close watch on your dog to prevent them from drinking natural water, and redirect their attention if they attempt to. Proper hydration is key to a safe and enjoyable boating experience.