Hey Fiah, you have a new mushroom island to the south of you, the approx location is -230, 3050. It's about what I guess would be average size for mushroom islands.
I had gone north after exploring that shoreline some distance to get my bearings and I ended up at Cape James (which has nothing to do with my username) where he put that marker of his. Then I went back down south (heading somewhat SW) to the 3km mark and ran into it.