Island turtle:

Cost - 8 turns, trainable at tc (doesn't require to be near water!), sacred spring.
Hp - 70, can't burn.
Attack - 14 (is not affected by nature upgrade)
Range - 1
Armor - 5/5
Speed - 2 (3 in water), can't move through forest tiles.
Carry capacity - 2 (can carry only same units ent warrior can)
Sight - 6
Spell resist - 50%
Bonuses: 50% bonus to ships and other sea units.
Abilities:
Shell on/off - transform ability: turtle gains +6/+6 armor (up to 11/11), 10 hp/turn regeneration and 100% spell resist at cost of 0 attack and 0 speed.
Additional info: all units inside instantly die if turtle dies. Regardless of place where turtle dies.
Can't enter into any transports: ships, wagons, zeppelins....
In very early game this unit will be a replacement of ent warriors