I built a large sandcastle.
The best indefinite article to use in the sentence is "a." The corrected sentence would be, "On the beach he built a huge sandcastle." This article is appropriate because it introduces a singular noun that is not previously specified.
The sandcastle is swept away.
Operation Sandcastle happened in 1955.
Yes, sandcastle is a common noun.
The cast of Sandcastle - 2013 includes: Katy Fullinwider
Sandcastle Water Park - Blackpool - was created in 1986.
Sandcastle Moat #21 is located on Polar Isle, on the beach on the southwestern end.
Sandcastle - 2010 II is rated/received certificates of: Singapore:NC-16
Yes the word sandcastles is a noun. It is the plural of sandcastle.
A castle you built out of sand
Hastle
Sandcastles