Complex sentence: They are not to be used to anchor a boat directly, as this will result in little to no holding power, since a mushroom anchor needs the proper amount of time to bury in the sediment.
Split into simpler sentences: They are not to be used to anchor a boat directly. Using a mushroom anchor in this way is an incorrect use of this type of anchor and will result in little to no holding power since a mushroom anchor needs the proper amount of time to bury in the sediment.