Adobe Photoshop
1 – Making the ocean
Set your foreground and background colours to a dark blue and a very dark blue.
Click Filter > Render > Clouds.
Create a new layer.
Set your colours to white and 50% gray (half way between black and white.)
Click Filter > Render > Clouds.
Click Filter > Distort > Ocean Ripple. Change the settings to give you reasonably sized waves.
Change the layer's Mode from Normal to Color Burn.
If you're not happy with the colours, go to your blue layer, and adjust the Brightness/Contrast and Hue/Saturation properties.
2 – Creating some islands
Create a new layer.
Draw and fill in several islands.
3 – Mountains and Sandy Beaches
In the Layers list, drag this layer below Layer 2, so it shares the Ocean Ripple effect.
In Layer Styles add a Shadow Bevel to make mountains.
Adjust the height of
the bevel, and the thickness of the outer glow
in Layer > Layer Styles >Scale Effect. Try adding in other effects
to enhance the drawing,
In Layer Styles and an outer glow to make the sandy beaches.
The glow will be whatever colour your background is set to.
Save your final picture.