happen that the anchor gets stuck under a rock or in another way. if that is so, then give it a few meters of line and tie it up firmly. then use the engine of the boat to pull the anchor in different directions to see if you can make it to come lose that way. do not give up too fast.
if you stop your engine at sea (or your engine fails and stops itself), the boat will automatically lay so it is in parallel with the waves, rolling from side to side and with high waves this can be feeling very unpleasant, but not necessarily dangerous unless too close 