As I understand it, SMBC has two map sets (SMB and SMBS), with certain "tagged" objects or enemies in each appearing or disappearing based on the character and difficulty, and the "tags" that an object can have are "Vertical Assist", "Horizontal Assist", "Poor Bowser Fighter", "Easy", and "Hard". I suggest adding an additional tag: "Water Assist". At the moment, this applies to Bass and Sophia. Bass can Double Jump and Dash-Jump, so he gets no assistance in the underwater levels that were designed for a character who can swim. On the other hand, Sophia can swim just as well as the Mario Bros., if not better, but gets completely unnecessary underwater platforms anyway. Those are the only two characters this is relevant to right now, but if Link's swimming and Simon's infinite underwater jumps are implemented (and I certainly hope they will be), then this will grow more significant. (By the way, this issue aside, the "tag" system is extremely helpful and well-implemented, and it is one of the most impressive additions to v3.0.) tl;dr: Some characters have very different mobility in water and out of water, and more will in the future (hopefully), so the "tag" system should reflect that.