At fairy islands, it is possible to Item Slide and build up enough speed to clip through the ground and touch the loading zone leading into the islands to get fairy rewards early. When attempting this trick, if Link doesn't clip through the island, then you didn't have enough speed and need to start further back or hold a smaller ESS position to charge up more speed during the Item Slide. If Link clips all the way through the island, your velocity was not aimed into the center of the island or you had too much speed and need to start further forward. Note: Getting a quiver or bomb bag early does not give you the bow or bombs as usable items.
Here is a picture depicting the island and what happens during the clip (or what happened when the clip failed):
To get past the tentacles blocking you from exiting Thorned Fairy simply do a (left) sidehop jumpslash and you should get boosted out of the tentacles. If you get stuck between the tentacles you can try to roll out or savewarp to put you back on the island
Using the pillar on the north side of the island, you can charge up an item slide enough to superswim away unlike other fairy islands. To properly time this superswim you should start the Item Slide when the water reaches its lowest level and begins to rise back up in its oscillation.