// Determines if the given grid is dangerous for the player to enter.
bool is_grid_dangerous(int grid);

        if (new_grid == DNGN_LAVA 
            || (new_grid == DNGN_DEEP_WATER && you.species != SP_MERFOLK))

        if (is_grid_dangerous(new_grid))

}
bool player_can_swim()
{
    return (you.species == SP_MERFOLK);

bool is_grid_dangerous(int grid)
{
    return (!player_is_levitating()
            && (grid == DNGN_LAVA
                || grid == DNGN_DEEP_WATER && !player_can_swim()));
}

    return (player_in_water() && you.species == SP_MERFOLK);

    return (player_in_water() && player_can_swim());

    if (you.species == SP_MERFOLK && player_is_swimming())

    if (player_is_swimming())

    const int mgrid = grd[monster->x][monster->y];

    swap = habitat_okay( monster, grd[loc_x][loc_y] );

    swap = habitat_okay( monster, grd[loc_x][loc_y] )
        && !is_grid_dangerous(mgrid);

    if (!swap)

    if (!swap && !is_grid_dangerous(mgrid))

#  [ds] If your map is not a minivault, make sure the side(s) that form the
#  border have a rock wall padding at least 6 deep. For instance, if your map
#  is ORIENT: north, you must have a 6 deep border of rock wall (or any
#  other kind of wall) along the northern, eastern, and western edges of the
#  map. If you're doing a fullscreen map (encompass), you must pad all around
#  the map with 6 layers of wall.

#  If your map is not a minivault, make sure the side(s) that form the border
#  have a rock wall padding at least 6 deep. For instance, if your map is
#  ORIENT: north, you must have a 6 deep border of rock wall (or any other kind
#  of wall) along the northern, eastern, and western edges of the map. If
#  you're doing a fullscreen map (encompass), you must pad all around the map
#  with 6 layers of wall. For ORIENT: encompass maps, you don't need to
#  explicitly include the padding provided you make the map small enough that
#  the padding can be provided automatically.

#  [dshaligram] All vaults MUST have an ORIENT: attribute; if there's no
#  ORIENT: attribute, the vault is considered to be a minivault, which is
#  usually not what you want.

#  All vaults MUST have an ORIENT: attribute; if there's no ORIENT: attribute,
#  the vault is considered to be a minivault, which is usually not what you
#  want.

#  Minivaults are handled very differently from regular vaults and special
#  levels. They're placed *after* normal map generation, whereas normal vaults
#  are placed before generating the rest of the level. There's no way to
#  guarantee generation of a minivault on a particular level, whereas vaults
#  can be forced to appear using a PLACE: attribute.
#
#  Floating vaults:
#  If you want to do vault-like things in a map that should be positioned like
#  a minivault, use ORIENT: float. This allows the vault to be placed in the
#  middle of a level, unlike normal vaults that must be anchored to at least
#  two edges of the map. Floating maps also do not need explicit entry points -
#  the dungeon builder will choose random entry points if you don't specify
#  any.
#

#  [ds] If your map is not a minivault, make sure the side(s) that form the
#  border have a rock wall padding at least 6 deep. For instance, if your map
#  is ORIENT: north, you must have a 6 deep border of rock wall (or any
#  other kind of wall) along the northern, eastern, and western edges of the
#  map. If you're doing a fullscreen map (encompass), you must pad all around
#  the map with 6 layers of wall.

#  If your map is not a minivault, make sure the side(s) that form the border
#  have a rock wall padding at least 6 deep. For instance, if your map is
#  ORIENT: north, you must have a 6 deep border of rock wall (or any other kind
#  of wall) along the northern, eastern, and western edges of the map. If
#  you're doing a fullscreen map (encompass), you must pad all around the map
#  with 6 layers of wall. For ORIENT: encompass maps, you don't need to
#  explicitly include the padding provided you make the map small enough that
#  the padding can be provided automatically.

#  [dshaligram] All special levels MUST have an ORIENT: attribute; if there's
#  no ORIENT: attribute, the level is considered to be a minivault, which is
#  usually not what you want.

#  All vaults MUST have an ORIENT: attribute; if there's no ORIENT: attribute,
#  the vault is considered to be a minivault, which is usually not what you
#  want.

#  Minivaults are handled very differently from regular vaults and special
#  levels. They're placed *after* normal map generation, whereas normal vaults
#  are placed before generating the rest of the level. There's no way to
#  guarantee generation of a minivault on a particular level, whereas vaults
#  can be forced to appear using a PLACE: attribute.
#
#  Floating vaults:
#  If you want to do vault-like things in a map that should be positioned like
#  a minivault, use ORIENT: float. This allows the vault to be placed in the
#  middle of a level, unlike normal vaults that must be anchored to at least
#  two edges of the map. Floating maps also do not need explicit entry points -
#  the dungeon builder will choose random entry points if you don't specify
#  any.
#