Coastal Climb is one of the obbies in Adopt Me! that can be accessed by going to the Playground and entering a small wooden building named 'obbies'. You complete this obby by jumping on wooden planks, climbing up rocks, avoiding red squares, and eventually exiting the same way you came in.
Previously, the reward for completing it as an adult was 21 Bucks and 15 Bucks as a baby. The cooldown period between a successful attempt and your next attempt is 45 minutes. However, you no longer receive Bucks after completing this obby and instead earn a badge.