10.1 is the lowest WalkSpeed a character (of any size without being scaled with :ScaleTo()) can have to be able to move in terrain water. However, if :ScaleTo() is called on a Player.Character, it will no longer be able to swim if its WalkSpeed is 10.1, and will only work if the WalkSpeed is increased. Note: Although the 10.1 WalkSpeed minimum for swimming has been the behavior since terrain water was added several years ago, this may be unintended behavior.
Reproduction:
Step 1: Set WalkSpeed to 10.1
Step 2: Swim in Terrain water
The character is able to swim
Step 3: Set Scale to 2
Step 4: Set WalkSpeed to 10.1
The character can no longer swim.
Water Bug.rbxl (52.8 KB)
Expected behavior
I expect the character to be able to move freely through terrain water if it is scaled with GetScale() as long as its WalkSpeed is above 10.