SB 5.26.5

ṛṣir uvāca
antarāla eva tri-jagatyās tu diśi dakṣiṇasyām adhastād bhūmer upariṣṭāc ca jalād yasyām agniṣvāttādayaḥ pitṛ-gaṇā diśi svānāṁ gotrāṇāṁ parameṇa samādhinā satyā evāśiṣa āśāsānā nivasanti.
Word for word: 
ṛṣiḥ uvāca — the great sage replied; antarāle — in the intermediate space; eva — certainly; tri-jagatyāḥ — of the three worlds; tu — but; diśi — in the direction; dakṣiṇasyām — southern; adhastāt — beneath; bhūmeḥ — on the earth; upariṣṭāt — a little above; ca — and; jalāt — the Garbhodaka Ocean; yasyām — in which; agniṣvāttā-ādayaḥ — headed by Agniṣvāttā; pitṛ-gaṇāḥ — the persons known as pitās; diśi — direction; svānām — their own; gotrāṇām — of the families; parameṇa — with great; samādhinā — absorption in thoughts of the Lord; satyāḥ — in truth; eva — certainly; āśiṣaḥ — blessings; āśāsānāḥ — desiring; nivasanti — they live.
Translation: 
The great sage Śukadeva Gosvāmī answered: All the hellish planets are situated in the intermediate space between the three worlds and the Garbhodaka Ocean. They lie on the southern side of the universe, beneath Bhū-maṇḍala, and slightly above the water of the Garbhodaka Ocean. Pitṛloka is also located in this region between the Garbhodaka Ocean and the lower planetary systems. All the residents of Pitṛloka, headed by Agniṣvāttā, meditate in great samādhi on the Supreme Personality of Godhead and always wish their families well.
Purport: 

As previously explained, below our planetary system are seven lower planetary systems, the lowest of which is called Pātālaloka. Beneath Pātālaloka are other planets, known as Narakaloka, or the hellish planets. At the bottom of the universe lies the Garbhodaka Ocean. Therefore the hellish planets lie between Pātālaloka and the Garbhodaka Ocean.