How many water elementals can control water affect?

[Hawkins]

The spell states, "When cast on water elementals and other water-based creatures, this spell acts as a slow spell (Will negates). The spell has no effect on other creatures." But there is no mention of how many "water elementals and other water-based creatures" cab be targeted.

[Howie23]

Sounds like you need to refer to the spell slow for specifics on how many are affected. Not sure if there are other issues by doing that.