Monks who follow the Way of the Tempest seek first to master themselves and the flow of battle by learning to emulate the chaos and destructive power of the storm, channeling their ki in ways that make them an unpredictable, hostile force. To a Tempest Monk, battle is not only a way to test their discipline, but a way to ride through the storm,

Steady Feet

By the time you commit yourself to this tradition at third level, your footing has become so sure and steady that you rarely find your feet being taken from you. You gain advantage on all saving throws against being pushed, shoved, pulled, or knocked prone. If an effect would push, pull, shove, or knock you prone, but doesn't allow a saving throw to resist it (such as the Warlock's Repelling Blast Invocation), you may make a Dexterity saving throw to resist such an effect, anyway (against the source's normal save DC, in the Repelling Blast example above, the saving throw would be made against the Warlock's Spell Save DC).
Spells that include forced movement as part of their effect in addition to damage are not exempt from this, and you may make an additional saving throw to resist the forced movement (You still take full damage, though).

Sure Footing

When selecting the Martial Tradition at third level, you have learned to keep yourself steady, even upon the most hostile ground. You ignore non-magical difficult terrain for purposes of movement and gain advantage on all Acrobatics attempts in order to maintain your balance and footing. Additionally, you may roll Acrobatics instead of Athletics to climb precarious surfaces, as you learn to mimic the movements of a sailor on the ratline.

Eye Of The Storm

Beginning at sixth level, whenever you successfully land an attack on an adjacent opponent with a Monk weapon or an Unarmed strike, you may spend a Ki point to strike a second adjacent foe with an Unarmed attack. There is no hard limit to how many times you can do this per turn, but an opponent cannot be attacked by the same Monk multiple times in one round using this technique.
A creature hit by Eye of the Storm may not use their Reaction to make Attacks of Opportunity on the Monk, and the Monk may make an Attack of Opportunity against them without spending their Reaction.

Home In Water

By eleventh level, while wearing no armour and carrying no shield, you gain the ability to move effortlessly through the water. as well as being able to hold your breath for an additional 3 minutes (add on to the usual 1 + con), you gain a swimming speed equal to your walking speed. By spending 2 ki points per creature and touching them, you can pass this benefit on to a willing creature for a number of minutes equal to your Wisdom modifier. They must still be wearing no armour and carrying no shields. If they don armour or a shield any time during this duration, the effect ends immediately and needs to be applied again if they later wish to gain its effects.

Sea Storms

When hit by lightning damage, flip a coin. tails you take half the damage, heads you take all the damage

Slippery Fighting

At seventeenth level, by spending 5 Ki points, you may use your Move action to move up to twice your speed without provoking attacks of opportunity. You may make one unarmed attack against all creatures adjacent to you at any point during this movement (moving past a Large creature will not allow you to attack them twice!). You may choose to have this attack deal Lightning damage instead of whatever type of damage your Unarmed attacks usually inflict. If you do, and the target is wet, the monk makes this attack with Advantage. If the target is immersed in salt water, not only does the attack automatically hit, but roll your Martial Arts damage die twice to determine damage.
Once the Monk uses this ability, they cannot use it again until they have completed a Long Rest..