It depends on what ruleset you are using, if you are using the FAQ 2010:
Attack Craft:
Attack craft are represented by 20mm square markers. When used in a wave, they must be spread and moved so they are always in contact with each other, and they cannot be stacked.
Attack craft waves must be assembled into the smallest circumference possible, such as a block of four, two rows of three, etc. For example, a single wave of eight ordnance markers cannot be stretched out into a single-file line eight markers long. On the other hand, individual markers not in a wave can be organized in any formation desired as long as no single marker moves farther from its launching vessel than its maximum possible movement.
Once separated, attack craft markers cannot be re-combined into waves.
Torpedoes:
A torpedo salvo (regardless of strength) is now represented with a Strength 3 marker with one or more D6 indicating the actual salvo strength. For specific dimensions, this marker should be no more than 2.5cm wide. Place the torpedo marker at the end of its movement in the turn of launch so that it is completely within the correct fire arc. Now retrace the markers movement, reducing its strength and conducting ordnance interactions as appropriate to prevent targeting vessels out of fire arc due to proximity,