Lightly oil an 8x8 inch baking dish with cooking spray or coconut oil. Sprinkle gelatin on top of ½ cup cold water in the bowl of a stand mixer fitted with the whisk attachment. Set aside to allow gelatin to bloom.
In a medium saucepan, combine granulated sugar, corn syrup, salt and ½ cup water and stir to combine. Bring to a boil over medium-high heat, swirling the pan occasionally, until the mixture reached 240°F on a candy thermometer, about 10-12 minutes.
With the mixer on low speed, very carefully pour hot syrup ino the gelatin mixture and mix until the gelatin is dissolved. Add the vanilla and coconut extract.
Gradually increase the speed to high (do this slowly so there is no splashing) and whip the mixture until very thick and stiff (it will also be white), about 8-10 minutes. Working quickly, pour the mixture into the prepared 8x8 inch pan. This will be very sticky, so you want to do it as quickly as possible. Use a spatula to help spread the mixture evenly in the pan. It doesn't have to be perfect on the top, and it will also settle as it sits.
Let sit uncovered until firm, about 4 hours at room temperature, or 2 hours in the fridge.
Once firm, dust a flat surface with a generous amount of confectioner's sugar, then use a butter knife to cut around the outside of the pan and unmold the marshmallow onto the work surface. You will likely have to use your hands to help pull it out, but it will come out in one piece.
Use a clean, sharp knife to cut the marshmallow into 16 pieces. Clean the knife between cuts, or spray with cooking spray to prevent it from sticking to the marshmallow too much. If there is excess cooking spray on the marshmallows, dab to remove with a paper towel.
Toss the cut marshmallows in confectioner's sugar, coating all sides. Shake off any excess, then dip the marshmallows into the melted dark chocolate and immediately dip the chocolate side of the marshmallow into the shredded coconut. Place on a sheet of wax paper to let cool at room temperature for an hour or in the fridge for 20 minutes. Remove from the wax paper and serve.