Change the rule, “Fire Control”, to read:

For a Vessel to Shoot (at a square) is for it to create a Shot at a square that is a Distance of up to that Vessel’s Range away from that Vessel’s square.

Distance is defined as the number of squares away, moving orthogonally, from one square’s center to another’s. (It’s a Manhattan distance.)

If Maritime Inaction has not been enacted, append the following to the above-mentioned rule:

A Battleship cannot Shoot at a square adjacent to the square it is located in. A Submarine can only Shoot at a square that falls in a straight line in the direction it is Facing.

As a Maritime(2) action, a Battleship can Shoot. As a Maritime action, a Submarine can Shoot.

If Maritime Inaction has been enacted, change “Have a Submarine they control Shoot at up to 1 square; this square must be between the Submarine and the grid edge the Submarine is Facing.”
to:

Have a Submarine they control Shoot at up to 1 square. (A Submarine can only Shoot at a square if it falls in a straight line in the direction it is Facing.)