The 'LSE-101' Curriculum:
Pool Etiquette Overview
General Awareness
Entering the Pool
Passing & Being Passed
Common Sense

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When passing...

An overtaking swimmer should gently but distinctly touch the feet of the swimmer being overtaken.  It may take two or three touches, but overtaking swimmers should not need to repeatedly slap or grab at the legs of a slower swimmer to politely make their presence known.

Swimmers enjoying a draft behind a strong lead swimmer, but who are just barely able to hold that pace should think twice before tagging the leader's toes and requesting to move ahead.  In such situations, it's highly unlikely that the (formerly) trailing swimmer will be able to hold the same pace for very long when leading without the draft.  This can lead to repeated "leap-frogging" and unnecessary contact, which can be annoying and disruptive for everyone in the lane.

Drafting swimmers not wishing to pass should swim far enough back from a lead swimmer that they don’t inadvertently touch the lead swimmer’s toes.  

Overtaking swimmers should not attempt to swim ‘wide’ past a slower swimmer—unless they are the only two swimmers in the lane—since in most cases this presents a hazard to other oncoming swimmer(s), forcing them to pull over to get out of the way.  

In the rare case that a passing swimmer does swim wide, s/he should be confident in his/her ability to sprint into the field of vision of the lead swimmer well before s/he gets to the wall.  Otherwise, this sets up for a collison at the wall as both swimmers attempt to turn on top of one another.  In the case of any ambiguity at the wall, the swimmer whose head is behind should give way to the swimmer whose head is in front.

In the equally rare case that a strong swimmer finds him or herself at the back of a line of several slower swimmers in circle format, it is acceptable (after looking carefully) to move to the other side of the lane mid-length and proceed in the opposite direction, somewhat ahead of the line s/he had been trailing.  This should only be done in cases where the lane is relatively crowded, where there are no other lanes moving at a more suitable pace, and where the process of tapping several swimmers in succession would be overly disruptive.  For anal-retentive swimmers fond of keeping detailed training logs, this move has the unfortunate disadvantage of completely messing up one's lap counts by introducing fractions.   :)

When being passed...

A lead swimmer who feels a touch on the feet from an overtaking swimmer, should continue to the next wall, then stop in the corner of the lane to let faster swimmer(s) past.  A single light touch may be accidental and can be ignored, but two or more distinct touches should be regarded almost universally as a request to swim through.

A swimmer who has been touched on the feet should move to a corner of the lane as soon as they get to the next wall in order to make way for passing swimmers turning there.  It's best if the touched/stopping swimmer moves immediately to the far left corner (from the perspective of an approaching swimmer), which would be the far right corner (from their own perspective looking back up the pool).  This routine applies as well to swimmers stopping of their own accord, (i.e., even if they haven't been tagged on the toes), since another swimmer who hasn't seen fit to touch toes may be right behind.

In circle format, swimmers should always stay aware of the gap behind them to the next swimmer, and try to anticipate when that swimmer (if s/he is faster) is likely to overtake him/her.  This is easily accomplished by looking back just before or during each turn, (whether 'flip' or 'open').

A lead swimmer who sees another swimmer coming up close behind as s/he turns at the wall should consider stopping and moving over immediately at that wall in order to let the faster swimmer past - rather than blocking that swimmer for an entire length to the next wall, creating a situation where toe-touching becomes necessary.

Swimmers being overtaken should never stop in the middle of the pool, nor should they continue beyond the next wall (e.g. back to the shallow end) after being ‘tagged’ on the feet.  Instead, they should stop at the next wall, at the corner of the lane.

If more than one swimmer is bunched close behind, the swimmer being overtaken should allow the entire group of faster swimmers to pass before pushing off the wall again (i.e. don’t push off right in front of someone else who’s also obviously faster.)

Swimmers being overtaken should not attempt to speed up (or slow down) once ‘tagged’, nor should they jump in and ‘tag back’ the new lead swimmer on the next lap.  

If two or more swimmers are closely matched in pace they should either position themselves at opposite ends of a lane (endless pursuit) or agree on how to share the lead.