As of V5.0, marines are no longer in SotIS.
A marine is part of category of units in SOTIS known as the side creeps. The marine is known to be the weakest side creep. The marine side creep comes in multiple groups : 2 marines and 1 Marauder, 2 Marines and 1 Viking, or 1 Marine, 1 Marauder and 1 Firebrat. A Marine starts with 384 health, Weapon speed of 0.3, Base damage of 3, Range of 5, 160 armor, and 2.25 movement speed.