In the context of future seabed underwater scientific observatories, a new Wi-Fi antenna (at 2.45 GHz) was recently developed for high data rate and short range wireless underwater applications. It supports real time video and rapid large file transmissions (54 Mb/s during experiments). Also its simplicity and compatibility with standard Wi-Fi equipment (modems, etc.) makes it a low cost solution for underwater applications. Therefore, while first prototypes have ever experimentally demonstrated the capabilities of the developed solution, several optimizations are possible. This paper focuses on size reduction and improvement to sea pressure resistance, bandwidth broadening, and a new antenna excitation which notably enable further height reduction.