A group of otters is called a romp. This term is often used to describe a group of otters when they are playing or frolicking in the water. Otters are known for their playful behavior, and seeing a romp of otters can be quite entertaining as they slide, dive, and chase each other.
Another term used for a group of otters is a bevy, especially when they are on land. However, romp is the more commonly used term and captures the lively and energetic nature of these adorable creatures.