योगवासिष्ठः yogavāsiṣṭhaḥ - book-5, chapter-44, verse-20

अन्तर्जलविधौ तस्मिन्विस्मृतध्यानमन्त्रधीः ।
पर्यस्तसंवित्प्रसरः सोऽपश्यज्जलमध्यतः ॥ २० ॥

antarjalavidhau tasminvismṛtadhyānamantradhīḥ ,
paryastasaṃvitprasaraḥ so'paśyajjalamadhyataḥ 20

20. antarjalavidhau tasmin vismṛtadhyānamantradhīḥ
paryastasaṃvitprasaraḥ saḥ apaśyat jalamadhyataḥ

20. tasmin antarjalavidhau vismṛtadhyānamantradhīḥ
paryastasaṃvitprasaraḥ saḥ jalamadhyataḥ apaśyat

20. During that underwater immersion, he, whose mind had forgotten the meditation (dhyāna) and mantra, and whose stream of consciousness was disrupted, saw (something) from the midst of the water.

Words meanings summery:

• अन्तर्जलविधौ (antarjalavidhau) - in the underwater ritual/process

• तस्मिन् (tasmin) - in that

• विस्मृतध्यानमन्त्रधीः (vismṛtadhyānamantradhīḥ) - whose intellect had forgotten meditation and mantra

• पर्यस्तसंवित्प्रसरः (paryastasaṁvitprasaraḥ) - whose stream of consciousness was disturbed/overthrown

• सः (saḥ) - Refers to the king. (he, that (one))

• अपश्यत् (apaśyat) - he saw

• जलमध्यतः (jalamadhyataḥ) - from the middle of the water

Words meanings and morphology

अन्तर्जलविधौ (antarjalavidhau) - in the underwater ritual/process

(noun)

Locative, masculine, singular of antarjalavidhi

antarjalavidhi - underwater ritual, rule for being underwater

Compound type : tatpuruṣa (antarjala+vidhi)

• antarjala – underwater
  adjective (neuter)
• vidhi – rule, method, ritual, ordinance
  noun (masculine)
  From root 'dhā' with prefix 'vi'
  Prefix: vi
  Root: dhā (class 3)

तस्मिन् (tasmin) - in that

(pronoun)

Locative, masculine, singular of tad

tad - that

विस्मृतध्यानमन्त्रधीः (vismṛtadhyānamantradhīḥ) - whose intellect had forgotten meditation and mantra

(adjective)

Nominative, masculine, singular of vismṛtadhyānamantradhī

vismṛtadhyānamantradhī - having forgotten meditation (dhyāna) and mantra in one's intellect

Compound type : bahuvrīhi (vismṛta+dhyāna+mantra+dhī)

• vismṛta – forgotten, not remembered
  adjective (neuter)
  Past Passive Participle
  Derived from root 'smṛ' (to remember) with prefix 'vi'
  Prefix: vi
  Root: smṛ (class 1)
• dhyāna – meditation, contemplation (dhyāna)
  noun (neuter)
  Action Noun
  From root 'dhyai' (to meditate)
  Root: dhyai (class 1)
• mantra – sacred utterance, hymn, spell (mantra)
  noun (masculine)
  From root 'man' (to think) + 'tra' suffix
  Root: man (class 4)
• dhī – intellect, understanding, mind, wisdom
  noun (feminine)
  From root 'dhyai' (to think, meditate)
  Root: dhyai (class 1)

Note: Refers to the subject ('saḥ').

पर्यस्तसंवित्प्रसरः (paryastasaṁvitprasaraḥ) - whose stream of consciousness was disturbed/overthrown

(adjective)

Nominative, masculine, singular of paryastasaṃvitprasara

paryastasaṁvitprasara - having a disturbed or overthrown flow of consciousness

Compound type : bahuvrīhi (paryasta+saṃvit+prasara)

• paryasta – thrown down, disturbed, overthrown, scattered
  adjective (neuter)
  Past Passive Participle
  From root 'as' (to throw) with prefix 'pari'
  Prefix: pari
  Root: as (class 4)
• saṃvit – consciousness, knowledge, understanding
  noun (feminine)
  From root 'vid' (to know) with prefix 'sam'
  Prefix: sam
  Root: vid (class 2)
• prasara – flow, stream, course, extension
  noun (masculine)
  Action Noun
  From root 'sṛ' (to flow) with prefix 'pra'
  Prefix: pra
  Root: sṛ (class 1)

Note: Refers to the subject ('saḥ').

सः (saḥ) - Refers to the king. (he, that (one))

(pronoun)

Nominative, masculine, singular of tad

tad - that, he, she, it

Masculine nominative singular

अपश्यत् (apaśyat) - he saw

(verb)

3rd person , singular, active, past imperfect (laṅ) of dṛś

Imperfect Tense

Third person singular imperfect active indicative

Root: dṛś (class 1)

जलमध्यतः (jalamadhyataḥ) - from the middle of the water

(indeclinable)

Formed from 'jalamadhya' (middle of water) + 'tas' (ablative suffix)

Compound type : tatpuruṣa (jala+madhya)

• jala – water
  noun (neuter)
• madhya – middle, center
  noun (neuter)

Note: Ablative meaning 'from'.