You conjure up a sphere of water with a 5-foot radius at a point you can see within range. The sphere can hover but no more than 10 feet off the ground. The sphere remains for the spell’s duration.
Any creature in the sphere’s space must make a Strength saving throw. On a successful save, a creature is ejected from that space to the nearest unoccupied space of the creature’s choice outside the sphere. A Huge or larger creature succeeds on the saving throw automatically, and a Large or smaller creature can choose to fail it. On a failed save, a creature is restrained by the sphere and is engulfed by the water. At the end of each of its turns, a restrained target can repeat the saving throw, ending the effect on itself on a success.
The sphere can restrain as many as four Medium or smaller creatures or one Large creature. If the sphere restrains a creature that causes it to exceed this capacity, a random creature that was already restrained by the sphere falls out of it and lands prone in a space within 5 feet of it.
As an action, you can move the sphere up to 30 feet in a straight line. If it moves over a pit, a cliff, or other drop-off, it safely descends until it is hovering 10 feet above the ground. Any creature restrained by the sphere moves with it. You can ram the sphere into creatures, forcing them to make the saving throw.
When the spell ends, the sphere falls to the ground and extinguishes all normal flames within 30 feet of it. Any creature restrained by the sphere is knocked prone in the space where it falls. The water then vanishes.
* - (a droplet of water)
If another player used conjure animals to fill this watery sphere with swarms of quippers... Would they count against the number of restrained targets? Technically they're just inhabiting the watery sphere.
So, it seems to me that RAW, that yes, it would count. However, Swarm of Quippers can, because they are a swarm, can fill the same space as other creatures: "Swarm. The swarm can occupy another creature's space and vice versa..." in that case it would maybe be more accurate to ask how much the sphere could lift? If I was the DM, I'd not count the swarm towards how many creatures the sphere could restrain and allow this combo, because this is too neat to not allow.
Hell yeah! Except RAW that would mean the Druid would become Restrained, but if I was a DM I would ignore that!
A situational spell
Transport:
Pity that there's other low level spells that can do similar but not exactly the same
Battle:
Does it block line of sight? In a 10 foot corridor could you even get past it? How does it squeeze through tight spaces? If you drop it off a cliff over 600 ft that takes longer than one round to drop you can dispel it before it hits?
Its a nice flavor spell, but honestly, not worth a 4th level spellslot.
There are way better lower level spells that do the same thing, only difference you cant move the Victims, but is that ability really woth using a 4th instead of a 2nd Level slot?