Learn Spanish (Spain): Prohíben que los bañistas entren al vestuario descalzos. - They prohibit the bathers from entering the changing room barefoot.

The main verb is prohibir (to prohibit), which is a verb of influence or command. When you have a verb like this followed by que and a change of subject (from the unnamed 'they' to los bañistas), it triggers the subjunctive in the second verb.

Why does prohíben have an accent mark?

The accent on the í breaks the natural vowel blend (diphthong) that would happen with the vowels o and i sitting next to each other around the silent h. This forces the spoken stress onto the í, making it pro-HÍ-ben.

Why is the word for 'bathers' masculine (los bañistas) if it ends in '-a'?

Spanish nouns ending in -ista (like turista or artista) use the exact same word for both men and women. You just change the article to match the person. Here, los bañistas refers to a group of men or a mixed-gender group.

Why does the sentence use al vestuario instead of just el vestuario?

Unlike in English where you 'enter a room' directly, the Spanish verb entrar requires a preposition before the destination, usually a or en. Here, a combines with the masculine article el to form the contraction al.