With its innovative free dive functions and dedicated Free dive mode, Suunto D4i is also perfect if you're serious about breath-hold diving. Programmed to sample depth three times a second, Suunto D4i records highly accurate data on the true depth reached. Using the Suunto Deep Stop RGBM algorithm, Suunto D4i enables continuous decompression for optimal ascent time. For deeper dives, the Deep Stop option adds further protection with a series of deep stops between your maximum depth and ceiling. You can test upcoming dives and view no-decompression time data for different depths before getting in the water with the built-in dive planner. After your dive, you can easily transfer your dive data to your computer for further analysis using the optional Suunto DM4 software, which includes a detailed logbook featuring a graphical representation of all your dives. Download cable sold separate.If you are into scuba diving you might want to add a scuba wireless transmitter.The Suunto Wireless tank pressure transmitter gives you current tank pressure and remaining air time with just a glance at your wrist. Before your dive, simply pair the transmitter with your dive computer and you’re good to go. The transmitter’s handy green LED light lets you know that it’s on.