This is a Destroy mission (see type of mission). The Aliens have emerged from the water and are attacking the small fishing ports and boats. Since your unit is located near one of the invasion front, you have been called to help stop or at least slow the invaders.
The environment is composed of small fishing ports, boats, beaches, rocky cliffs. Fishermen are running around, completely panicked. A few get their guns out and are trying to attack the aliens.
On to the Forest level