海天気.jp is a comprehensive weather forecasting application designed specifically for marine activities. It provides pinpoint weather forecasts for over 8,000 marine spots across Japan, offering detailed predictions for up to 84 hours with hourly updates on weather conditions, wind, temperature, and wave heights. The app visually represents precipitation with an intuitive umbrella icon, making it easy to gauge expected rainfall at a glance.

In addition to short-term forecasts, users can access a 14-day weather outlook updated every three hours, which aids in planning marine leisure activities. The app also features animated visualizations of raincloud and lightning movements for both past and future scenarios, ensuring users stay informed about changing weather conditions. Additional resources include tide data, sea temperature maps, and current location routing for fishing spots, enhancing the overall user experience.