Critique this spell please? Land Legs, meant for merfolk

[Shpadoinkle]

Land Legs
Alteration
Sor/wiz, Clr/Ora, Level ? (This is mostly what I'm looking for help with)
Range: Close (25' + 5'/2 caster level)
Target: 1 merfolk per caster level
Duration: 24 hours (D)
Saving throw: Will negates (harmless)
SR: Yes

This spell transforms the fishlike tail of merfolk into a pair of humanlike legs. Those affected lose their Swim speed and racial bonus to Swim checks, but gain a land movement speed of 30'(? Open to changing this, maybe 25'.) Those affected by this spell can end this effect voluntarily.

This spell may also be able to affect non-merfolk characters who lack legs (such as naga,) though this is up to DM discretion.

Merfolk and locathah are one of the nations in a setting I'm creating, where they're kind of different castes of the same race and nation. Merfolk dwell in the sea and large inland lakes and serve as the governing faction, with most of the nation's spellcasters being merfolk, while locathah tend to live in and around rivers and wetlands and essentially serve as the nation's peasant class, doing the majority of the physical work, as well as serving as the nation's armed forces. Merfolk developed this spell to make travel over land, if necessary, easier.

The closest existing counterpart to this spell is Water Breathing, which is more powerful because it grants those affected by it an ability they don't have. Merfolk already have a very slow land speed (only 5' by default, though the Strongtail alternate racial trait increases that to 15', while lowering their swim speed to 30') this just increases it, while also costing them their racial bonus to Swim checks and their Swim speed - while affected by this, a merfolk is no better at swimming than a human with the same stats and skill points in the Swim skill is.

I was aiming for this being a level 1 spell for primary casters like clerics and wizards, am I overlooking something that makes this obviously more powerful than that?

[Kurald Galain]

The massive duration AND multi-target effect is what makes this a game changer for aquatic humanoids, and that's why I'd say this shouldn't be a first-level spell.

The closest matches here are probably Alter Self (2nd level) and Expeditious Retreat (1st level) but both of those last only one minute per level, and affect one creature. I'd say as a 1st-level spell make this self-only and one hour per level; or as a 2nd-level spell make it target one creature and last all day; or as 3rd-level spell make it work as it is written now.

(edit) Also I'd say this fits the Druid list better than the Cleric list; I'm not sure why this would be a Cleric spell at all, except in certain domains. Wizard list is suitable, of course.

[Rynjin]

I'd say call it a 2nd level spell...and remove the (D). Once cast you're locked in for 24 hours.

This is the same approach a similar spell Ignoble Form takes.

[Quentinas]

I'm not an expert of pathfinder but a quick search found this spell Fins to feet So considering this spell in game your version should probably be a 4th or 5th level spell (as the duration is quite big and is a multiple spell) , but as I said I'm not an expert of pathfinder

[Rynjin]

I'm not an expert of pathfinder but a quick search found this spell Fins to feet So considering this spell in game your version should probably be a 4th or 5th level spell (as the duration is quite big and is a multiple spell) , but as I said I'm not an expert of pathfinder

Fins to Feet being 3rd is another good indicator that this should be 2nd (minus the (D) tag), as Fins to Feet is a much better spell (it has effectively no drawbacks).

I missed that Land Legs was multitarget though. It should definitely be single target with its current effect.

[Beni-Kujaku]

I would, too, say 2nd level for single target, 3rd or 4th for multi-target, and no (D)