Dive computers in accordance with embodiments of the invention are disclosed. One embodiment includes a mobile phone handset, including a microprocessor, a microphone connected to the microprocessor, a speaker connected to the microprocessor, a telephone transceiver connected to the microprocessor, memory, a display, and an external connector for communicating with external devices wherein the memory contains a software application, and a waterproof housing including a pressure transducer, where the mobile phone handset is located within the waterproof housing and connected to the pressure transducer via the external connector, and wherein the software application configures the mobile phone handset to create a dive log stored in memory, wherein the dive log comprises recorded information including depth of submersion information recorded from the pressure transducer and display the recorded information during the dive.