What about adding some subtypes?
Tortle
* Ability Score Increase. You can increase 1 attribute by 2, and another by 1. Typically these are Strength and Wisdom.
* Age. Young tortles crawl for a few weeks after birth before learning to walk on two legs. They reach adulthood by the age of 25 and live an average of 250 years.
* Alignment. Tortles tend to lead orderly, ritualistic lives. They develop customs and routines, becoming more set in their ways as they age. Most are lawful good. A few can be selfish and greedy, tending more toward evil, but it's unusual for a tortle to shuck off order in favor of chaos.
* Size. Tortle adults stand 5 to 6 feet tall and average 450 pounds. Their shells account for roughly one-third of their weight. Your size is Medium.
* Speed. Your base walking speed is 30 feet and you have a swim speed of 15 feet
* Claws. Your claws are natural weapons, which you can use to make unarmed strikes. If you hit with them, you deal slashing damage equal to 1d4 + your Strength modifier, instead of the bludgeoning damage normal for an unarmed strike.
* Hold Breath. You can hold your breath for up to 1 hour at a time.
* Natural Armor.Your shell provides ample protection, however; it gives you a base AC of 17 (your Dexterity modifier doesn't affect this number). If you are using a shield, you can apply the shield's bonus as normal.
Custom plate armor can be made that increases this, but other kinds of armor do not generate significant benefits.
* Shell Defense. You can withdraw into your shell as an reaction to being hit or failing a saving throw. If you do so, these effects apply to the triggering attack or saving throw. Until you emerge, you gain 3/4 cover (a +5 bonus to AC and reflex saving throws), and you have advantage on Strength and Constitution saving throws. While in your shell, you are prone (but attackers within 5' do not have advantage on attacks against you), your speed is 0 and can't increase, you have disadvantage on Dexterity saving throws, you can't take reactions, and the only action you can take is to emerge from your shell.
* Survival Instinct. You gain proficiency in the Survival skill. Tortles have finely honed survival instincts.
* Languages. You can speak, read, and write Common and Aquan.
Snapping
You have a huge head and jaws, and are typically smaller than most Tortles.
Your bite is a natural weapon that deals 1d6+strength damage. You can use it as a bonus action or as a reaction to taking damage.
You can take reactions even if you are surprised.
Leatherback
Your swimming speed is 40 feet, you can drink salt water, and you can hold your breath for up to 2 hours, and your lifespan is up to 500 years.
Due to the softness of your shell, your Natural Armor only grants 14 AC, but you can add up to 2 points of Dexterity to it. You gain +1 HP per level and have powerful build. Custom heavy armor can be used to replace this AC.
Leaf
The Leaf turtles live come from a great forest, and their shell looks like a large leaf.
When you make an wisdom ability check and you wouldn't add your proficiency bonus to the roll, instead add 1/2 of your proficiency bonus. If you already add your proficiency bonus, add 1.
You learn one Druid cantrip, and at 3rd level you can pick a 1st level druid spell. You know that spell, and can cast it once per day without expending a spell slot.
Map
Map turtles are known for wandering and exploring. Their shell has hexagonal patterns on it. Traditionally Map turtles carve their shells with images of the areas they have visited.
When you make an intelligence ability check or saving throw and you wouldn't add your proficiency bonus to the roll, instead add 1/2 of your proficiency bonus. If you already add your proficiency bonus, add 1.
You learn one Bard cantrip, and at 3rd level you can pick a 1st level Bard spell. You know that spell, and can cast it once per day without expending a spell slot.
Mud
Mud turtles have a brown shell. You have a burrow speed of 10' in sand or dirt and tremorsense with a 10' range.
Tortle
* Ability Score Increase. You can increase 1 attribute by 2, and another by 1. Typically these are Strength and Wisdom.
* Age. Young tortles crawl for a few weeks after birth before learning to walk on two legs. They reach adulthood by the age of 25 and live an average of 250 years.
* Alignment. Tortles tend to lead orderly, ritualistic lives. They develop customs and routines, becoming more set in their ways as they age. Most are lawful good. A few can be selfish and greedy, tending more toward evil, but it's unusual for a tortle to shuck off order in favor of chaos.
* Size. Tortle adults stand 5 to 6 feet tall and average 450 pounds. Their shells account for roughly one-third of their weight. Your size is Medium.
* Speed. Your base walking speed is 30 feet and you have a swim speed of 15 feet
* Claws. Your claws are natural weapons, which you can use to make unarmed strikes. If you hit with them, you deal slashing damage equal to 1d4 + your Strength modifier, instead of the bludgeoning damage normal for an unarmed strike.
* Hold Breath. You can hold your breath for up to 1 hour at a time.
* Natural Armor.Your shell provides ample protection, however; it gives you a base AC of 17 (your Dexterity modifier doesn't affect this number). If you are using a shield, you can apply the shield's bonus as normal.
Custom plate armor can be made that increases this, but other kinds of armor do not generate significant benefits.
* Shell Defense. You can withdraw into your shell as an reaction to being hit or failing a saving throw. If you do so, these effects apply to the triggering attack or saving throw. Until you emerge, you gain 3/4 cover (a +5 bonus to AC and reflex saving throws), and you have advantage on Strength and Constitution saving throws. While in your shell, you are prone (but attackers within 5' do not have advantage on attacks against you), your speed is 0 and can't increase, you have disadvantage on Dexterity saving throws, you can't take reactions, and the only action you can take is to emerge from your shell.
* Survival Instinct. You gain proficiency in the Survival skill. Tortles have finely honed survival instincts.
* Languages. You can speak, read, and write Common and Aquan.
Snapping
You have a huge head and jaws, and are typically smaller than most Tortles.
Your bite is a natural weapon that deals 1d6+strength damage. You can use it as a bonus action or as a reaction to taking damage.
You can take reactions even if you are surprised.
Leatherback
Your swimming speed is 40 feet, you can drink salt water, and you can hold your breath for up to 2 hours, and your lifespan is up to 500 years.
Due to the softness of your shell, your Natural Armor only grants 14 AC, but you can add up to 2 points of Dexterity to it. You gain +1 HP per level and have powerful build. Custom heavy armor can be used to replace this AC.
Leaf
The Leaf turtles live come from a great forest, and their shell looks like a large leaf.
When you make an wisdom ability check and you wouldn't add your proficiency bonus to the roll, instead add 1/2 of your proficiency bonus. If you already add your proficiency bonus, add 1.
You learn one Druid cantrip, and at 3rd level you can pick a 1st level druid spell. You know that spell, and can cast it once per day without expending a spell slot.
Map
Map turtles are known for wandering and exploring. Their shell has hexagonal patterns on it. Traditionally Map turtles carve their shells with images of the areas they have visited.
When you make an intelligence ability check or saving throw and you wouldn't add your proficiency bonus to the roll, instead add 1/2 of your proficiency bonus. If you already add your proficiency bonus, add 1.
You learn one Bard cantrip, and at 3rd level you can pick a 1st level Bard spell. You know that spell, and can cast it once per day without expending a spell slot.
Mud
Mud turtles have a brown shell. You have a burrow speed of 10' in sand or dirt and tremorsense with a 10' range.
