The walking speed modifier cheat only lets you enter two characters, which means you can only enter whole numbers because the decimal counts. Being able to enter three or four would allow for increasing or decreasing your speed by only a bit.
The cheat also doesn’t seem to affect you while you’re diving (as in, when your character turns into a round shadow and you can swim again, not during the diving animation itself).

(By the way, love the plugin so so much! Thank you for your hard work!)