Let's do the surface first.
Some of the cells contain the whole word PIT.
H | O | S | PIT | A | L | PIT | T | E | R | |
O | P | E | A | E | ||||||
P | U | L | PIT | E | PIT | A | P | H | S | |
E | I | S | O | S | PIT | |||||
D | O | N | T | PIT | Y | M | E | E | ||
E | F | I | K | |||||||
J | H | I | T | Z | F | E | L | D | ||
U | PIT | R | E | E | E | |||||
PIT | V | I | P | E | R | S | PIT | E | S | |
E | N | S | U | PIT | ||||||
R | O | O | T | N | I | P | P | L | E |
1. Setting for House or Grey's Anatomy: HOSPITAL
3. Device for removing avocado interiors: PITTER
7. Preacher's position: PULPIT
8. Inscriptions on tombstones: EPITAPHS
10. 1978 single from Faith Hope and Charity: DON'T PITY ME
13. Coach/Olympian/mathematician Ottmar: HITZFELD
16. Crotaline serpent: PIT VIPER
17. Irritates maliciously: SPITES
18. Board game featuring Eyrie Dynasties and Lizard Cult: ROOT
19. Cover this with a pasty: NIPPLE
1. Aspired or expected: HOPED
2. Requires reticulation before you can play SimCity: SPLINE
4. Sends a message via pipes or prison cell wall: TAPS
5. Chance to collect oneself: RESPITE
6. Personify, embody: EPITOMIZE
9. British fighter planes of the 1940s (or hot-tempered people): SPITFIRES
11. Don't stop now! You'll get there!: KEEP IT UP
12. Jollity-bearing planet: JUPITER
14. Notwithstanding: DESPITE
15. Red Storm coach Rick: PITINO
Next, let's do the underwater part.
These are HARD TO CONSTRUCT.
P | R | O | F | E | S | S | O | R | A | L |
E | P | L | E | B | E | M | I | D | J | I |
M | O | U | S | E | R | S | C | R | U | B |
M | E | A | G | A | N | D | H | O | N | I |
E | X | C | E | L | I | K | I | N | G | S |
F | E | R | M | O | E | N | O | L | A | |
E | N | M | I | T | Y | L | E | A | R | N |
N | I | F | T | Y | A | D | O | R | E | D |
U | E | M | A | T | S | U | B | E | T | A |
E | V | E | N | I | R | E | G | N | A | L |
M | A | N | E | P | O | P | P | I | N | S |
The cells that correspond to the PIT cells in the surface puzzle—the places the Creature might pull you down into—spell the answer, FOSSIL FUEL.