No armor or shields
One-handed melee weapons
Hand crossbows only

Your Strength score increases by 2, and your Constitution score increases by 1.

Your tough exterior shell acts like natural armor.  Your AC is 15 + your Dexterity modifier.  However, due to your non-humanoid body shape, you cannot utilize manufactured armor or shields.

One of your claws is much larger and stronger than the other.  You may use to attack, dealing 1d6 plus your strength modifier in bludgeoning damage.  On a successful hit, you may use a bonus action to grapple your opponent.  Finally, any actions taken using this claw make strength checks at an advantage.  

Your smaller claw can be used to manipulate objects and wield one-handed melee weapons.  Attacks made by weapons held in this smaller claw are considered off-hand attacks, therefore ability modifiers are not added to weapon damage.  Also, due to your unique anatomical structure, you are unable to use any ranged weapons other than hand crossbows.

Your oceanic upbringing taught you how to survive predators and other dangers.  You have proficiency in Stealth and Survival.

Young Explorer Crabs reach adulthood by age 7 and may live to a little over 100 years.

Explorer Crabs stand approximately 3 feet tall and are 4-5 feet wide.  Their weight ranges fromm 130 to 170 pounds,.  Your size is Medium.

You can move quickly and gracefully through a variety of terrains and environments.  Your walking speed is 30, your climbing speed is 20, and your swimming speed is 40.

You  are able to breath Air and Water.

You can see in dim light within 60 feet of you as if it were bright light and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

You can speak, read, and write Aquan and Common.