U

in the swim

verb (used without object), swam, swum, swim·ming.

to move in water by movements of the limbs, fins, tail, etc.
to float on the surface of water or some other liquid.
to move, rest, or be suspended in air as if swimming in water.
to move, glide, or go smoothly over a surface.
to be immersed or steeped in or overflowing or flooded with a liquid: eyes swimming with tears.
to be dizzy or giddy; seem to whirl: My head began to swim.

verb (used with object), swam, swum, swim·ming.

to move along in or cross (a body of water) by swimming: to swim a lake.
to perform (a particular stroke) in swimming: to swim a sidestroke.
to cause to swim or float, as on a stream.
to furnish with sufficient water to swim or float.

noun

an act, instance, or period of swimming.
a motion as of swimming; a smooth, gliding movement.

Idioms

in the swim, alert to or actively engaged in events; in the thick of things: Despite her age, she is still in the swim.

verb swims, swimming, swam or swum

(intr) to move along in water, etc, by means of movements of the body or parts of the body, esp the arms and legs, or (in the case of fish) tail and fins
(tr) to cover (a distance or stretch of water) in this way
(tr) to compete in (a race) in this way
(intr) to be supported by and on a liquid; float
(tr) to use (a particular stroke) in swimming
(intr) to move smoothly, usually through air or over a surface
(intr) to reel or seem to reelmy head swam; the room swam around me
(intr; often foll by in or with) to be covered or flooded with water or other liquid
(intr often foll by in) to be liberally supplied (with)he’s swimming in money
(tr) to cause to float or swim
(tr) to provide (something) with water deep enough to float in
swim against the tide or swim against the stream to resist prevailing opinion
swim with the tide or swim with the stream to conform to prevailing opinion

noun

the act, an instance, or period of swimming
any graceful gliding motion
a condition of dizziness; swoon
a pool in a river good for fishing
in the swim informal fashionable or active in social or political activities

Old English swimman “to move in or on the water, float” (class III strong verb; past tense swamm, past participle swummen), from Proto-Germanic *swemjanan (cf. Old Saxon and Old High German swimman, Old Norse svimma, Dutch zwemmen, German schwimmen), from PIE root *swem- “to be in motion.”

The root is sometimes said to be restricted to Germanic, but possible cognates are Welsh chwyf “motion,” Old Irish do-sennaim “I hunt,” Lithuanian sundyti “to chase.” For the usual Indo-European word, see natatorium. Sense of “reel or move unsteadily” first recorded 1670s; of the head or brain, from 1702. Figurative phrase sink or swim is attested from mid-15c., often with reference to ordeals of suspected witches.

1540s, “the clear part of any liquid” (above the sediment), from swim (v.). Meaning “part of a river or stream frequented by fish” (and hence fishermen) is from 1828, and is probably the source of the figurative meaning “the current of the latest affairs or events” (1869).

Actively participating, in the thick of things, as in He was new in town, but he soon got in the swim at school. This expression alludes to the fishing term for a large number of fish in one area, a so-called swim. [Mid-1800s]

In addition to the idioms beginning with swim

swim against the current
swim with the tide

also see:

in the swim
sink or swim