To improve the communication quality and reduce the bit error rate（BER）of tilted multiple-input single-output underwater wireless optical communication（T-MISO-UWOC）systems, a spherical T-MISO-UWOC（ST-MISO-UWOC）system model was proposed. Through theoretical analysis and numerical simulations, the differences between the ST-MISO-UWOC system and the conventional T-MISO-UWOC system in key performance metrics such as BER, received optical power, and Q-factor were investigated. Simulation results show that under a signal-to-noise ratio（SNR）of 20 dB, a transmission distance of 1.5 m, and a data rate of 12 Gb/s, the BER of the ST-MISO-UWOC system is as low as 3.09×10^-12, which is five orders of magnitude lower than that of the conventional system（8.08×10^-7）. Additionally, the ST-MISO-UWOC system exhibits significantly improved stability in optimal decision timing, higher received optical power, and stronger adaptability in high-speed and long-distance transmissions.