The most common and most likely answer to this crossword clue is the 5 letter word LIDOS
I've seen this crossword clue in The Guardian
L
I
D
O
S
More clues leading to the result LIDOS
- These beaches could be packed solid
- One closes loop — how synergy begins, where people take the plunge
- Nothing tops lying around swimming pools
- Solid rocks in pools
- Where to find swimmers showing promise in class on regular basis
- Cover over very large leisure facilities
- Extremely uplifting wearing cap — swimmers like them
Buddy explains!

The straight part
We know that "where people take the plunge" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case where people take the plunge = lidos.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does LIDOS mean?
LIDOS noun- Part of the sea by a beach sectioned off for swimming and other aquatic activities.
- An outdoor swimming pool.