You can check out this forum thread in relation to the same issues
Have you checked out the relevant Wiki pages, quests, maps, videos, guides, walkthroughs & hidden gifts.
You can easily find the solutions to puzzles if you check out the walkthroughs & maps.....everything is clearly & concisely highlighted.... including hidden gifts.
In this scenario it is much more easier to consult, study & follow the maps.....instead of the videos.
The Wiki maps show that the cannons need to be fired in ALL positions in game mine "Diggys Pirate Bay".
Even though in the 4th game scene of "Diggys Pirate Bay" there is no skeleton to fire the cannon at.....you still need to fire the cannon the extra time to gain the extra rock.
In the game mine of "Diggys Pirate Bay" there are multiple hidden gifts to be found:
1️⃣ 1st game scene place 3 rocks on 3 shell piles.
2️⃣ 3rd game scene place 3 rocks on 3 shell piles.
3️⃣ 4th game scene place 8 rocks on 8 shell piles
4️⃣ 5th game scene place 7 rocks on 7 shell piles.
5️⃣ 6th game scene there are 3 different sequences of placements for the 5 wine barrels.
6️⃣ 7th game scene place 4 rocks on 4 shell piles.
VIDEO - PC
VIDEO - Mobile
Fan based websites