jsonize swim speed modifier as per walk cost mutation modifier

data/json/mutations/mutations.json

@@ -1789,6 +1789,7 @@
     "category": [ "CHIMERA", "RAPTOR", "LIZARD" ],
     "prereqs": [ "SKIN_ROUGH" ],
     "changes_to": [ "THICK_SCALES", "SLEEK_SCALES" ],
+    "movecost_swim_modifier": 0.9,
     "wet_protection": [
       { "part": "HEAD", "ignored": 3 },
       { "part": "LEG_L", "ignored": 10 },
@@ -1842,6 +1843,7 @@
     "types": [ "SKIN" ],
     "prereqs": [ "SCALES" ],
     "category": [ "FISH" ],
+    "movecost_swim_modifier": 0.75,
     "wet_protection": [
       { "part": "HEAD", "good": 7 },
       { "part": "LEG_L", "good": 21 },
@@ -3134,6 +3136,7 @@
     "prereqs": [ "TAIL_STUB" ],
     "category": [ "FISH" ],
     "wet_protection": [ { "part": "LEG_L", "good": 3 }, { "part": "LEG_R", "good": 3 } ],
+    "movecost_swim_modifier": 0.75,
     "restricts_gear": [ "LEG_L", "LEG_R" ],
     "allow_soft_gear": true
   },
@@ -3818,6 +3821,7 @@
     "prereqs": [ "STR_UP", "STR_UP_2", "STR_UP_3", "STR_UP_4" ],
     "leads_to": [ "HIBERNATE" ],
     "category": [ "URSINE" ],
+    "movecost_swim_modifier": 0.95,
     "armor": [ { "parts": "ALL", "bash": 1 } ],
     "movecost_modifier": 1.05
   },
@@ -5681,6 +5685,7 @@
     "description": "Your legs have transformed into six tentacles.  This decreases your speed on land by 20%, makes your movement silent, increases your swimming speed, and reduces wet penalties.",
     "types": [ "LEGS" ],
     "leads_to": [ "LEG_TENT_BRACE" ],
+    "movecost_swim_modifier": 0.85,
     "category": [ "CEPHALOPOD" ],
     "wet_protection": [
       { "part": "LEG_L", "neutral": 21 },
@@ -5974,6 +5979,7 @@
     "description": "You're as comfortable in water as on land, and your body has adapted around that fact.  Your base swimming speed is greatly increased, and weight will hinder you much less while swimming.",
     "category": [ "FISH" ],
     "threshreq": [ "THRESH_FISH" ],
+    "movecost_swim_modifier": 0.45,
     "purifiable": false
   },
   {

src/character.cpp

@@ -5010,6 +5010,7 @@ mutation_value_map = {
     { "max_stamina_modifier", calc_mutation_value_multiplicative<&mutation_branch::max_stamina_modifier> },
     { "weight_capacity_modifier", calc_mutation_value_multiplicative<&mutation_branch::weight_capacity_modifier> },
     { "hearing_modifier", calc_mutation_value_multiplicative<&mutation_branch::hearing_modifier> },
+    { "movecost_swim_modifier", calc_mutation_value_multiplicative<&mutation_branch::movecost_swim_modifier> },
     { "noise_modifier", calc_mutation_value_multiplicative<&mutation_branch::noise_modifier> },
     { "overmap_sight", calc_mutation_value_multiplicative<&mutation_branch::overmap_sight> },
     { "overmap_multiplier", calc_mutation_value_multiplicative<&mutation_branch::overmap_multiplier> },

src/mutation.h

@@ -140,6 +140,7 @@ struct mutation_branch {
         float max_stamina_modifier = 1.0f;
         float weight_capacity_modifier = 1.0f;
         float hearing_modifier = 1.0f;
+        float movecost_swim_modifier = 1.0f;
         float noise_modifier = 1.0f;
         float scent_modifier = 1.0f;
         cata::optional<int> scent_intensity;

src/mutation_data.cpp

@@ -335,6 +335,7 @@ void mutation_branch::load( const JsonObject &jo, const std::string & )
     optional( jo, was_loaded, "movecost_modifier", movecost_modifier, 1.0f );
     optional( jo, was_loaded, "movecost_flatground_modifier", movecost_flatground_modifier, 1.0f );
     optional( jo, was_loaded, "movecost_obstacle_modifier", movecost_obstacle_modifier, 1.0f );
+    optional( jo, was_loaded, "movecost_swim_modifier", movecost_swim_modifier, 1.0f );
     optional( jo, was_loaded, "attackcost_modifier", attackcost_modifier, 1.0f );
     optional( jo, was_loaded, "max_stamina_modifier", max_stamina_modifier, 1.0f );
     optional( jo, was_loaded, "weight_capacity_modifier", weight_capacity_modifier, 1.0f );

src/player.cpp

@@ -176,7 +176,6 @@ static const bionic_id bio_synaptic_regen( "bio_synaptic_regen" );
 static const bionic_id afs_bio_linguistic_coprocessor( "afs_bio_linguistic_coprocessor" );
 
 static const trait_id trait_ACIDBLOOD( "ACIDBLOOD" );
-static const trait_id trait_AMPHIBIAN( "AMPHIBIAN" );
 static const trait_id trait_ANTENNAE( "ANTENNAE" );
 static const trait_id trait_ANTLERS( "ANTLERS" );
 static const trait_id trait_CANNIBAL( "CANNIBAL" );
@@ -758,12 +757,9 @@ int player::swim_speed() const
     float hand_bonus_mult = ( usable.test( bp_hand_l ) ? 0.5f : 0.0f ) +
                             ( usable.test( bp_hand_r ) ? 0.5f : 0.0f );
 
-    if( !has_trait( trait_AMPHIBIAN ) ) {
-        ret = 440 + weight_carried() / 60_gram - 50 * get_skill_level( skill_swimming );
-        /** AMPHIBIAN increases base swim speed */
-    } else {
-        ret = 200 + weight_carried() / 120_gram - 50 * get_skill_level( skill_swimming );
-    }
+    // base swim speed.
+    ret = ( 440 * mutation_value( "movecost_swim_modifier" ) ) + weight_carried() /
+          ( 60_gram / mutation_value( "movecost_swim_modifier" ) ) - 50 * get_skill_level( skill_swimming );
     /** @EFFECT_STR increases swim speed bonus from PAWS */
     if( has_trait( trait_PAWS ) ) {
         ret -= hand_bonus_mult * ( 20 + str_cur * 3 );
@@ -784,19 +780,6 @@ int player::swim_speed() const
     if( has_trait( trait_WEBBED ) ) {
         ret -= hand_bonus_mult * ( 60 + str_cur * 5 );
     }
-    /** @EFFECT_STR increases swim speed bonus from TAIL_FIN */
-    if( has_trait( trait_TAIL_FIN ) ) {
-        ret -= 100 + str_cur * 10;
-    }
-    if( has_trait( trait_SLEEK_SCALES ) ) {
-        ret -= 100;
-    }
-    if( has_trait( trait_LEG_TENTACLES ) ) {
-        ret -= 60;
-    }
-    if( has_trait( trait_FAT ) ) {
-        ret -= 30;
-    }
     /** @EFFECT_SWIMMING increases swim speed */
     ret += ( 50 - get_skill_level( skill_swimming ) * 2 ) * ( ( encumb( bp_leg_l ) + encumb(
                 bp_leg_r ) ) / 10 );