Simplify the following text for a Grade 5 native English-speaking person.
Original: Nudibranchs are often casually called `` sea slug '' , but many sea slugs belong to several taxonomic groups which are not related to nudibranchs . A number of these other sea slugs ( such as the colorful Aglajidae ) are often confused with nudibranchs .
Simplified: Nudibranchs are one of the groups which are informally known as sea slugs .