SC doubt about verb tense - 2

[reachdeepaky]

In page 261 of SC guide, we have the following:

Q 3) When he swam across the lake, he lay down on the far shore and relaxed in the sunshine until be was thoroughly dry

SC guide expln-> CORRECTION: When he HAD SWUM across the lake, he lay down on the far shore and relaxed in the sunshine until be was thoroughly dry

My Question:
a) I understand the explanation.
However in SC guide, we have the example - "She played with her friends when the baby sitter arrived". As per expln, 'played' took place after the 'baby sitter arrived'.
As per this expln, 'lay' and 'relaxed' should happen after 'swam' in Q3 and hence 'HAD SWUM' (past perfect) isn't really required. isn't it?

Please explain.

[tim]

Yes, "had swum" is required in order to denote that the process of swimming had been completed by the time everything else happened. This is not required with the babysitter example because an arrival is completed the moment it occurs. Arrival is not a process but rather an event..

[vikram4689]

When he HAD SWUM across the lake, he lay down on the far shore and relaxed in the sunshine until be was thoroughly dry

i think "when" has only 2 uses (is it correct ?):
a) modifying or defining a time period/event
b) for contemporaneous actions

"when" is above sentence is not used as b) because tense in "when" clause is different from tense in "main" clause. so, is the usage of "when" is to define a time period as in a)

[tim]

i think "when" in this case covers both (a) and (b)..

[vikram4689]

but for contemporaneous action, both clauses should happen at same time and, thus, be in same tense e.g. when i lie to my parents, i feel bad

in case at hand, swimming happened earlier than lay and relaxed happened

[tim]

yes but HAD SWUM occurred at the same time as LAY AND RELAXED. just ask yourself at what time on the clock you could make each of those statements and you'll see.. :)

[vikram4689]

i think read it too fast and didn't exactly comprehend what the sentence actually said. 2 questions,

a) (just to confirm) does following summarizes your reasoning: WHEN he HAD SWUM corresponds to a time by which swimming had already happened and now it is contemporaneous with LAY and RELAXED.
b) do the 2 uses of "when" encompass all possible variants of "when" tested on gmat

[tim]

a) yes
b) that seems like a safe assumption. nothing is a guarantee of course..