Ditto.
Apology accepted. Without challenge.
Such as The Cloudless Sky Returned (PeAu 45) (ArM5 p128)?
Or a 5e version of Neptune's Supplicant from Mythic Seas (p 77)? This would allow the magus to sail into the storm, but not the pursuers.
Here is my conversion -- note that the Mythic Seas 4e spell is ReAq 35, as opposed to ReAu 35 (see below). Feedback is welcome:
Neptune's Supplicant
ReAu 40
R: Touch, D: Sun, T: Group
Insert text from Mythic Seas p 77, but note that some 4e rules do not hold in 5e
This spell can be cast on a structure (e.g. boat) to protect against very severe weather phenomenon, such as hurricanes and tornadoes, or anything less severe.
(Base 10, +1 Touch, +2 Sun, +3 Structure)
And while we are at it, adjusting the above magic item effect for creating currents in the water, as a spell:
Sailor's Guide
R: Voice, D: Sun, T: Individual
ReAq 25
When cast, the target water begins to flow in the desired direction of the caster. The water flows in the same direction for the entire duration. This allows for considerably faster boat travel. When sailing, this spell can be a hindrance in combat, as there can be substantial loss of ship maneuverability. Changing direction of the current requires the spell to be cast again.
(Base 4, +2 Voice, +2 Sun, +1 Unnatural)
Control the Current
R: Voice, D: Concentration, T: Individual
ReAq 20
As Sailor's Guide, but the caster can change the direction of the water at will with a concentration ease factor of 3. This can be useful when having to deftly maneuver the ship, such as during combat. In combat, the concentration check should done with a stress die.
(Base 4, +2 Voice, +1 Concentration, +1 Unnatural)
I do not have the rule mechanics in the descriptions, since the 5e ship rules are not as detailed (looking at City and Guild) as Mythic Seas 4e. These spells give the traveling ships advantages in combat and would dramatically reduce travel times (and the associated weather variability).
Feedback is appreciated and I welcome rule mechanic suggestions.
EDIT: Updated above spells to include feedback from comment below by Troy.
EDIT: Neptune's Supplicant forgot the +1 touch. Updated.
Spells that change a current to any desired direction should in general have an "Unnatural" modifier. Unlike the wind which can normally travel from any direction, a current in a body of water has a far more limited range which can often be as narrow as only one or two directions.
Neptune's Supplicant would only ward against a "severe weather phenomenon" (Base 5), rather than a "very severe weather phenomenon" (Base 10). A hurricane would require the Base 10. Also since Neptune's Supplicant is a ward effect, you would need Target Structure to protect the whole ship and its crew. Spells that require more than one Target type in their design need to use the more expensive option. For this one you are warding/protecting a ship (Structure) against multiple types of weather phenomenons (Group). However since it is a Ward rather than Control effect, you do not need the +1 Precision requirement.
You might also consider a few different ReAq spells. Things like a Control effect which causes waves to break and part around the ship. Since waves are a real danger, this type of effect is really important since it will protect the ship from being swamped or broken in rough seas. You could also cast a Ward against water on the main hold, which would prevent water from entering the hold until it was damaged enough to break the ward. Don't ward the entire ship against water, you will get unintended side effects like being unable to having drinking water. As it is, you would have to store your drinking water outside of the main hold.
A PeAq Base 10 spell to destroy water can also be extremely helpful. While a bilge was not in use during the time of Mystic Europe, all ships collect water in their lowest compartment(s). While in general having some water in this area is not detrimental (and in fact is helpful) to ship operations, you really do not want it overflowing. Thus a spell which would destroy all of the water here. The same as the ward effect, you would be better served by target Room than target Structure. You also want a momentary rather than time duration.