The abbreviation (aq) in chemical equations or symbols simply means that this material is present in water as a homogeneous phase. The state symbol has nothing to do with the actual and true "structure" in solution. In short forget about hydration shell.
From IUPAC's recommendations "Notation for states and processes, significance of the word standard in chemical thermodynamics, and remarks on commonly tabulated forms of thermodynamic functions" Pure & Appl.Chem., Vol.54, No.6, pp. 1239—1250, 1982.
the symbol for a solution in which water is the solvent (an aqueous solution) is aq; in the past this symbol has sometimes been used to denote an infinitely dilute aqueous solution, but infinite dilution should henceforward be denoted by the extra symbol $\infty$.
$\ce{CO2 (aq)}$ would imply dissolved carbon dioxide in water (i.e.,to our eyes it is a single phase, just like an unopened bottle of coke).
$\ce{Br2 (aq)}$ would imply homogeneous solution of liquid bromine in water.
$\ce{NaCl (aq)}$: Salt dissolved in water.
A colloid is a heterogeneous phase.
But above all, do not worry too much about these minor symbolism issues. A chemical equation is not meant to convey everything. It is just a shorthand notation to describe chemical reactions. A real experiment or a research paper should describe the experimental condition with sufficient details in such a way that an experienced person should be able to repeat it.
You can also use (sln) as the state symbol, when the substance is dissolved but not present in water. From the same document, I quote an example.
$$\ce{Na (s) + 5C2H5OH (l) = 0.5 H2 (g) + \{C2H5ONa + 4 C2H5OH\} (sln)}$$
Try to interpret it and see if it makes sense.