The most common and most likely answer to this crossword clue is the 4 letter word SWIM
I've seen this crossword clue in The Guardian
S
W
I
M
More clues leading to the result SWIM
- Where you'll see Victoria and Mike bathe
- Be immersed with wife in computer game
- Travel by sea perhaps from Cornwall? One mile
- Bits of salami were in Mexican dip
- Characters predominantly seen working in milk float
- Fancy missing hour after second reel
- Introduces sturdy walkway into marshland – the alternative is to sink
- Regularly saw firms dip
- Group of women wearing two costume sizes for pool activity
- Dip primarily served with Indian meals
Buddy explains!

The straight part
We know that "dip" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dip = swim.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 SWIM mean?
SWIM noun- An act or instance of swimming.
- The sound, or air bladder, of a fish.
- A part of a stream much frequented by fish.
- A dance move of the 1960s in which the arms are moved in a freestyle swimming manner.
- To move through the water, without touching the bottom; to propel oneself in water by natural means.
- To become immersed in, or as if in, or flooded with, or as if with, a liquid
- To move around freely because of excess space.
- To traverse (a specific body of water, or a specific distance) by swimming; or, to utilize a specific swimming stroke; or, to compete in a specific swimming event.
- To cause to swim.
- To float.
- To be overflowed or drenched.
- To immerse in water to make the lighter parts float.
- To test (a suspected witch) by throwing into a river; those who floated rather than sinking were deemed to be witches.
- To glide along with a waving motion.
- A dizziness; swoon.
- To be dizzy or vertiginous; have a giddy sensation; to have, or appear to have, a whirling motion.
- Abbreviation of someone who isn't me. used as a way to avoid self-designation or self-incrimination, especially in online drug forums