Fathoms witches are those who see magic as an ever flowing current, a river of power and knowledge and secrets that ever runs around and through all things, ebbing and flowing like the tide, and with depths beyond the fathoming of mortals. They are at home amidst the seas, able to shape their bodies to better be at home in the waters, and like the waters of the world excel at the duality of creation and destruction, giving and taking life.
When you take this archetype at 2nd level you add all spells of the water school to your list of witch spells.
You may also cast the alter self spell at will without expending a spell slot even if it isn't prepared, but only choosing the Amphibious option when doing so, and you may turn the benefits on and off for the duration as an action instead of being able to choose a different one. When you do so, the same benefits apply to your familiar.
At 6th level whenever you cast a spell that restores hit points, you may add your spellcasting ability modifier to one healing roll for that spell.
At 10th level you gain resistance to your choice of lightning, cold, or acid damage, and can change which type whenever you finish a short or long rest. In addition, whenever you finish a long rest you are surrounded by a thin shield of water that absorbs incoming damage, granting you temporary hit points equal to your witch level + your spellcasting ability modifier.
Finally, when you cast the free Amphibious alter self spell granted by Annointed by the Waves, it no longer requires concentration.
At 14th level, you add the lightning bolt spell to your witch spell list. You always have the geyser blast, scalding steam, lightning bolt, and steal breath spells prepared, they do not count against your number of witch spells prepared, and you may cast each of these once per long rest at the lowest spell level without expending a spell slot.