diff -ru -X /home/jjm/cvs/no.freeciv FreecivCVS/client/climisc.c freeciv/client/climisc.c
--- FreecivCVS/client/climisc.c	Sun Mar 12 23:32:57 2000
+++ freeciv/client/climisc.c	Fri Apr 21 14:08:10 2000
@@ -240,13 +240,15 @@
 	 && tile_is_known(i,j)>=TILE_KNOWN_FOGGED
 	 && map_get_terrain(i,j)!=T_OCEAN) {
 	con = map_get_continent(i,j);
-	if(this_con==-1) {
-	  ptile->continent = this_con = con;
-	} else if(con != this_con) {
-	  freelog(LOG_DEBUG, "renumbering client continent %d to %d at (%d %d)",
-		  con, this_con, x, y);
-	  climap_renumber_continent(i, j, this_con);
-	  recycle_continent_num(con);
+	if(con>0) {
+	  if(this_con==-1) {
+	    ptile->continent = this_con = con;
+	  } else if(con != this_con) {
+	    freelog(LOG_DEBUG, "renumbering client continent %d to %d at (%d %d)",
+		    con, this_con, x, y);
+	    climap_renumber_continent(i, j, this_con);
+	    recycle_continent_num(con);
+	  }
 	}
       }
     }
@@ -255,7 +257,6 @@
     ptile->continent = new_continent_num();
     freelog(LOG_DEBUG, "new client continent %d at (%d %d)",
 	    ptile->continent, x, y);
-    return;
   }
 }
 
diff -ru -X /home/jjm/cvs/no.freeciv FreecivCVS/client/packhand.c freeciv/client/packhand.c
--- FreecivCVS/client/packhand.c	Sun Apr 16 10:39:07 2000
+++ freeciv/client/packhand.c	Fri Apr 21 14:08:10 2000
@@ -332,6 +332,9 @@
   if(game.player_ptr->ai.control && !ai_manual_turn_done) user_ended_turn();
 }
 
+/**************************************************************************
+...
+**************************************************************************/
 void handle_before_new_year(void)
 {
   clear_notify_window();
@@ -972,6 +975,7 @@
 void handle_tile_info(struct packet_tile_info *packet)
 {
   struct tile *ptile = map_get_tile(packet->x, packet->y);
+  enum tile_terrain_type old_terrain = ptile->terrain;
   enum known_type old_known = ptile->known;
   int tile_changed = 0;
 
@@ -994,9 +998,24 @@
   }
 
   /* update continents */
-  if(packet->known >= TILE_KNOWN_FOGGED && old_known == TILE_UNKNOWN
-     && ptile->terrain != T_OCEAN) {
+  if ((packet->known >= TILE_KNOWN_FOGGED &&
+       old_known == TILE_UNKNOWN && ptile->terrain != T_OCEAN) ||
+      ((old_terrain == T_OCEAN) && (ptile->terrain != T_OCEAN))) {
+    /* new knowledge or new land -- update can handle incrementally */
     climap_update_continents(packet->x, packet->y);
+  } else if (old_known >= TILE_KNOWN_FOGGED &&
+	     ((old_terrain != T_OCEAN) && (ptile->terrain == T_OCEAN))) {
+    /* land changed into ocean -- rebuild continents map from scratch */
+    int x, y;
+    for (y = 0; y < map.ysize; y++)
+      for (x = 0; x < map.xsize; x++)
+	map_set_continent(x, y, 0);
+    climap_init_continents();
+    for (y = 0; y < map.ysize; y++)
+      for (x = 0; x < map.xsize; x++)
+	if ((tile_is_known(x, y) >= TILE_KNOWN_FOGGED) &&
+	    (map_get_terrain(x, y) != T_OCEAN))
+	  climap_update_continents(x, y);
   }
 
   /* refresh tiles */
diff -ru -X /home/jjm/cvs/no.freeciv FreecivCVS/common/map.c freeciv/common/map.c
--- FreecivCVS/common/map.c	Sun Mar 12 23:32:58 2000
+++ freeciv/common/map.c	Fri Apr 21 14:08:10 2000
@@ -662,6 +662,21 @@
 /***************************************************************
 ...
 ***************************************************************/
+static void clear_infrastructure(int x, int y)
+{
+  map_clear_special(x, y, S_ROAD);
+  map_clear_special(x, y, S_IRRIGATION);
+  map_clear_special(x, y, S_RAILROAD);
+  map_clear_special(x, y, S_MINE);
+  map_clear_special(x, y, S_POLLUTION);
+  map_clear_special(x, y, S_FORTRESS);
+  map_clear_special(x, y, S_FARMLAND);
+  map_clear_special(x, y, S_AIRBASE);
+}
+
+/***************************************************************
+...
+***************************************************************/
 void map_irrigate_tile(int x, int y)
 {
   enum tile_terrain_type now, result;
@@ -678,6 +693,8 @@
   }
   else if(result!=T_LAST) {
     map_set_terrain(x, y, result);
+    if (result==T_OCEAN)
+      clear_infrastructure(x, y);
     reset_move_costs(x, y);
   }
   map_clear_special(x, y, S_MINE);
@@ -697,6 +714,8 @@
     map_set_special(x, y, S_MINE);
   else if(result!=T_LAST) {
     map_set_terrain(x, y, result);
+    if (result==T_OCEAN)
+      clear_infrastructure(x, y);
     reset_move_costs(x, y);
   }
   map_clear_special(x,y, S_FARMLAND);
@@ -715,6 +734,8 @@
   
   if (result != T_LAST) {
     map_set_terrain(x, y, result);
+    if (result==T_OCEAN)
+      clear_infrastructure(x, y);
     reset_move_costs(x, y);
   }
 
diff -ru -X /home/jjm/cvs/no.freeciv FreecivCVS/common/unit.c freeciv/common/unit.c
--- FreecivCVS/common/unit.c	Thu Apr 20 14:33:45 2000
+++ freeciv/common/unit.c	Fri Apr 21 14:08:10 2000
@@ -963,9 +963,11 @@
 	( (ptile->terrain==type->mining_result && 
 	   !(ptile->special&S_MINE)) ||
 	  (ptile->terrain!=type->mining_result &&
-	   type->irrigation_result!=T_LAST &&
+	   type->mining_result!=T_LAST &&
 	   (ptile->terrain!=T_OCEAN ||
-	    can_reclaim_ocean(punit->x, punit->y))) )) {
+	    can_reclaim_ocean(punit->x, punit->y)) &&
+	   (type->mining_result!=T_OCEAN ||
+	    !(map_get_city(punit->x, punit->y)))) )) {
       unit_list_iterate(ptile->units, tunit) {
 	if(tunit->activity==ACTIVITY_IRRIGATE) return 0;
       }
@@ -986,7 +988,9 @@
 	  (ptile->terrain!=type->irrigation_result &&
 	   type->irrigation_result!=T_LAST &&
 	   (ptile->terrain!=T_OCEAN ||
-	    can_reclaim_ocean(punit->x, punit->y))) )) {
+	    can_reclaim_ocean(punit->x, punit->y)) &&
+	   (type->irrigation_result!=T_OCEAN ||
+	    !(map_get_city(punit->x, punit->y)))) )) {
       unit_list_iterate(ptile->units, tunit) {
 	if(tunit->activity==ACTIVITY_MINE) return 0;
       }
@@ -1051,6 +1055,8 @@
 	   (ptile->terrain!=type->transform_result) &&
 	   (ptile->terrain!=T_OCEAN ||
 	    can_reclaim_ocean(punit->x, punit->y)) &&
+	   (type->transform_result!=T_OCEAN ||
+	    !(map_get_city(punit->x, punit->y))) &&
 	   unit_flag(punit->type, F_TRANSFORM);
 
   default:
diff -ru -X /home/jjm/cvs/no.freeciv FreecivCVS/data/default/terrain.ruleset freeciv/data/default/terrain.ruleset
--- FreecivCVS/data/default/terrain.ruleset	Sun Apr 16 08:55:10 2000
+++ freeciv/data/default/terrain.ruleset	Fri Apr 21 14:08:10 2000
@@ -234,9 +234,9 @@
 irrigation_result    = "Plains"
 irrigation_food_incr = 0
 irrigation_time      = 5
-mining_result        = "no"
+mining_result        = "Swamp"
 mining_shield_incr   = 0
-mining_time          = 0
+mining_time          = 15
 transform_result     = "Grassland"
 transform_time       = 24
 helptext	     = _("\
@@ -522,8 +522,8 @@
 mining_result        = "Forest"
 mining_shield_incr   = 0
 mining_time          = 15
-transform_result     = "Plains"
-transform_time       = 24
+transform_result     = "Ocean"
+transform_time       = 36
 helptext	     = _("\
 Swamps suffer from an over-abundance of water, making agriculture\
  somewhat problematic.\
diff -ru -X /home/jjm/cvs/no.freeciv FreecivCVS/server/gamelog.c freeciv/server/gamelog.c
--- FreecivCVS/server/gamelog.c	Sun Jan  2 06:32:15 2000
+++ freeciv/server/gamelog.c	Fri Apr 21 14:39:23 2000
@@ -68,7 +68,10 @@
   va_start(args, message);
   my_vsnprintf(buf, sizeof(buf), message, args);
   if (level==GAMELOG_MAP){
-    fprintf(fs,"%s\n",buf);
+    if (buf[0] == '(')  /* KLUGE!! FIXME: remove when we fix the gamelog format --jjm */
+      fprintf(fs,"%i %s\n", game.year,buf);
+    else
+      fprintf(fs,"%s\n",buf);
   } else if (level==GAMELOG_EOT){
     fprintf(fs,"*** %s\n",buf);
   } else {
diff -ru -X /home/jjm/cvs/no.freeciv FreecivCVS/server/unitfunc.c freeciv/server/unitfunc.c
--- FreecivCVS/server/unitfunc.c	Thu Apr 20 12:13:08 2000
+++ freeciv/server/unitfunc.c	Fri Apr 21 14:42:11 2000
@@ -39,6 +39,7 @@
 #include "civserver.h"
 #include "gamelog.h"
 #include "gotohand.h"
+#include "mapgen.h"		/* assign_continent_numbers */
 #include "maphand.h"
 #include "plrhand.h"
 #include "settlers.h"
@@ -1749,7 +1750,8 @@
 /**************************************************************************
   For each city adjacent to (x,y), check if landlocked.  If so, sell all
   improvements in the city that depend upon being next to an ocean tile.
-  (Should be called after any terrain changes.  Assumes no city at (x,y).)
+  (Should be called after any ocean to land terrain changes.
+   Assumes no city at (x,y).)
 **************************************************************************/
 static void city_landlocked_sell_coastal_improvements(int x, int y)
 {
@@ -1791,6 +1793,27 @@
 }
 
 /**************************************************************************
+  Checks for terrain change between ocean and land.  Handles side-effects.
+  (Should be called after any potential ocean/land terrain changes.)
+**************************************************************************/
+static void check_terrain_ocean_land_change(int x, int y,
+					    enum tile_terrain_type old)
+{
+  enum tile_terrain_type new = map_get_terrain(x, y);
+
+  if ((old == T_OCEAN) && (new != T_OCEAN)) {
+    /* ocean to land ... */
+    city_landlocked_sell_coastal_improvements(x, y);
+    assign_continent_numbers();
+    gamelog(GAMELOG_MAP, "(%d,%d) land created from ocean", x, y);
+  } else if ((old != T_OCEAN) && (new == T_OCEAN)) {
+    /* land to ocean ... */
+    assign_continent_numbers();
+    gamelog(GAMELOG_MAP, "(%d,%d) ocean created from land", x, y);
+  }
+}
+
+/**************************************************************************
   progress settlers in their current tasks, 
   and units that is pillaging.
   also move units that is on a goto.
@@ -1883,8 +1906,9 @@
   if (activity==ACTIVITY_IRRIGATE) {
     if (total_activity (punit->x, punit->y, ACTIVITY_IRRIGATE) >=
         map_build_irrigation_time(punit->x, punit->y)) {
+      enum tile_terrain_type old = map_get_terrain(punit->x, punit->y);
       map_irrigate_tile(punit->x, punit->y);
-      city_landlocked_sell_coastal_improvements(punit->x, punit->y);
+      check_terrain_ocean_land_change(punit->x, punit->y, old);
       unit_activity_done = 1;
     }
   }
@@ -1908,8 +1932,9 @@
   if (activity==ACTIVITY_MINE) {
     if (total_activity (punit->x, punit->y, ACTIVITY_MINE) >=
         map_build_mine_time(punit->x, punit->y)) {
+      enum tile_terrain_type old = map_get_terrain(punit->x, punit->y);
       map_mine_tile(punit->x, punit->y);
-      city_landlocked_sell_coastal_improvements(punit->x, punit->y);
+      check_terrain_ocean_land_change(punit->x, punit->y, old);
       unit_activity_done = 1;
     }
   }
@@ -1917,8 +1942,9 @@
   if (activity==ACTIVITY_TRANSFORM) {
     if (total_activity (punit->x, punit->y, ACTIVITY_TRANSFORM) >=
         map_transform_time(punit->x, punit->y)) {
+      enum tile_terrain_type old = map_get_terrain(punit->x, punit->y);
       map_transform_tile(punit->x, punit->y);
-      city_landlocked_sell_coastal_improvements(punit->x, punit->y);
+      check_terrain_ocean_land_change(punit->x, punit->y, old);
       unit_activity_done = 1;
     }
   }