Concept:
In coding-decoding questions, each letter may shift a fixed number of positions in the alphabet.
Step 1: Analyze the pattern in the given code.
"WATER" becomes "YCVGT".
Each letter is shifted +2 positions forward in the alphabet.
\[
W \rightarrow Y
\]
\[
A \rightarrow C
\]
\[
T \rightarrow V
\]
\[
E \rightarrow G
\]
\[
R \rightarrow T
\]
Step 2: Apply the same rule to "FIRE".
\[
F \rightarrow H
\]
\[
I \rightarrow K
\]
\[
R \rightarrow T
\]
\[
E \rightarrow G
\]
Step 3: Write the coded word.
\[
\boxed{\text{HKTG}}
\]