In this vector background tutorial, we will be learning on how to make this marine tiles effect with the transform tool.
Making the Tiles
You will need a harmonic colour scheme to match your pattern. Copy and paste suitable colour palette it to your document. Next, draw a rounded square by holding shift to constrain the proportion. Use the colour picker to pick the turquoise colour from the colour palette.
Navigate to Effect>Distort & Transform>Transform. Choose 15 copies and increase horizontal to 55 pt to leave gaps in between the tiles. Click OK. This will create a row of horizontal tile.
Navigate to Effect>Distort & Transform>Transform again. Choose 15 copies and increase vertical to -55pt to tile it vertically.
Colouring with Various Tones
Expand the transformation to recolour the tiles. Navigate to Object>Expand Appearance to expand the pattern. Click Ctrl/command+G 2 times to ungroup the tiles. Choose some random tiles and use the colour picker to picker a lighter tone.
Repeat the steps above to set different random tones to your pattern.
Resize the tiles randomly. Navigate to Object>Transform>Transform Each. Set both horizontal and vertical scale to 90%.
Choose some random tiles you want to transform and press Ctrl/Command+D to repeat the previous transformation again to the tiles. This will resize it 90% smaller. Press Ctrl/Command+D a few more times to make the tiles smaller. Here is the final tiles pattern.