Hi! I've been inspired by the individual known as B Jake, who used to post monster Mondays here, but no longer does. He's still writing up more and going strong with them every week, and you can find them here https://bjacobt1.wixsite.com/monstermonday
This week's entry: Gyrapedes. Imagine if a centipede could curl up its body and roll around exactly like Sonic the Hedgehog. (Insert Pokemon reference here.) That was the initial inspiration for this creature.
That's cool.
Since it has a swim speed, is he supposed to use it while rolling?
No, the thing can legitimately swim! So if it's ever interrupted while out on the water, it can still get back to shore. However, if a player were to make it stop rolling while it's on the water because they think it might not be able to swim, I may conveniently "forget" that it can swim.