Backport from the 1.19.3 1.3.0 version.
Added a new "Simulation V2" mode(new default setting). Allows the cape to move left and right slightly, prevents too-hard bends/cape clipping into itself, and entirely new underwater physics and behavior(unlike before, where it failed like the vanilla Minecraft cape). Fixed a lot of edge cases, where the cape would become oddly thin, tilted, or inverted. Using the Wind Mode "Waves" will now slow down while underwater.
Full Changelog: https://github.com/tr7zw/WaveyCapes/compare/1.2.2-1.19.3...1.3.0-1.19.3