Here is the full list of all 12 Iron Sea Defenders trophies - there are 7 bronze, 4 silver and 1 gold.
Complete level when your castle has 1 HP
Complete all levels with 3 stars
Kill 500 enemies with the secret weapon
Sell 500 towers
Build 1000 towers
Fully upgrade 200 towers
Get 100 000 coins
Launch 100 waves on one map manually
Sell 50 towers
Kill 1000 enemies
Build 50 towers
Kill 50 000 enemies