diff --git a/src/lang/english.txt b/src/lang/english.txt
index 31a87d6262..1e781370e0 100644
--- a/src/lang/english.txt
+++ b/src/lang/english.txt
@@ -5012,6 +5012,7 @@ STR_ERROR_TUNNEL_RAMP_TOO_SHORT                                 :{WHITE}... ramp
 STR_ERROR_TUNNEL_TOO_MANY                                       :{WHITE}... too many tunnels
 STR_ERROR_NO_DRILLING_ABOVE_CHUNNEL                             :{WHITE}No oil rigs allowed above underwater tunnels.
 STR_ERROR_ANOTHER_TUNNEL_IN_THE_WAY_FOR_CHUNNEL                 :{WHITE}Three tiles are needed to pass under the other tunnel.
+STR_ERROR_CHUNNEL_ONLY_OVER_SEA                                 :{WHITE}Underwater tunnels are only allowed to cross sea...
 
 # Object related errors
 STR_ERROR_TOO_MANY_OBJECTS                                      :{WHITE}... too many objects
diff --git a/src/tunnelbridge_cmd.cpp b/src/tunnelbridge_cmd.cpp
index f86a3e84a3..0ed3a53db0 100644
--- a/src/tunnelbridge_cmd.cpp
+++ b/src/tunnelbridge_cmd.cpp
@@ -734,9 +734,10 @@ CommandCost CmdBuildTunnel(TileIndex start_tile, DoCommandFlag flags, uint32 p1,
 
 				end_tile += delta;
 				tiles++;
+				if (IsTileType(end_tile, MP_WATER) && IsSea(end_tile)) is_chunnel = true;
 			}
 			/* The water was passed */
-			is_chunnel = true;
+			if (!is_chunnel) return_cmd_error(STR_ERROR_CHUNNEL_ONLY_OVER_SEA);
 			head_tiles = 0;
 			found_tunnel_tile = INVALID_TILE;
 		}