Submarine Sea, is the 1st underwater hidden stage of SR that requires 100% wins to be unlocked (but not the only) if you don't have a good DPS thunder, fire or physical weapon, this stage is a piece of cake, if not, it won't be so easy But this stage should really be tried, since it decreases your AGI by 30% if won, this means 100/0.7 ~ +43% DPS!