# How to draw “wavy” sequence of boxes

I'm very new to TikZ and I'm having a slight problem that I'm not entirely sure how to solve.

Suppose I generate a sequence of boxes like so:

 \documentclass{report}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\foreach \x in {1,2,...,5}{
\draw (\x,0) -- (\x+1,0) -- (\x+1,1) -- (\x,1) -- cycle;
}
\end{tikzpicture}
\end{document}


How can I introduce a "wavy" effect to the sequence such the the boxes fit within the following shape:

 \documentclass{report}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\draw (0,0) .. controls (2.5,0.5) and (7.5,-0.5) .. (10,0) -- (10,1) .. controls (7.5,0.5) and (2.5,1.5) .. (0,1) -- cycle;
\end{tikzpicture}
\end{document}


I also want to colour these boxes using fill=, so I need for them to be recognised independent entities.

If you know the curve of your wave, you can use the plot command from tikz. I assume that it is not essential to use the spline that you gave in your MWE, so I replaced it with a sine wave that looks similar:

\begin{tikzpicture}
\foreach \x in {1,2,...,5} {
\draw (\x,0) .. controls (\x+0.25,0.5) and (\x+0.75,-0.5) .. (\x+1,0) -- (\x+1,1)  .. controls (\x+0.75,0.5) and (\x+0.25,1.5) .. (\x,1) -- cycle;
}
\end{tikzpicture}


Then, one just has to use the same function to plot the boxes:

\begin{tikzpicture}
\draw[domain=0:10] (0,0) -- plot (\x,{0.2*sin(\x*36)}) -- plot (10-\x,{1-0.2*sin(\x*36)}) -- cycle;
\end{tikzpicture}