Flipperform

1st-level biomancy* (ritual)

Casting Time: 1 action
Range: 30 feet
Components: V, S, M (a fish’s fin)
Duration: 1 hour
Class: Druid, Ranger, Sorcerer, Tamer, Wizard

You change the morphology of a willing creature within range. It grows webbed fingers and gains a swimming speed equal to its walking speed.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, you can affect one additional creature for each slot level above 1st. In addition, the duration of the spell doubles for each slot level above 1st.

*can be replaced with transmutation
Source: Heliana's Guide to Monster Hunting