Here is the full list of all 51 Summer in Mara achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
The sea is dangerous, next time get back to your boat before getting tired.
Build all the main structures on Home Island.
Complete all the quests from Taima.
Complete all the quests from Pilly, Milly & Tilly.
Complete all the quests from Litio.
Complete all the quests from Ecco.
Complete all the quests from Aquila.
Get all the Koa's outfits.
Complete all the quests from Mûn.
Pay the mortgage on your boat.
Complete all the quests from Napopo.
Defeat the Elit.
Recover all the chrystalis from the Door.
Complete all the quests from Blu.
Complete all the quests from Rigatta.
Catch one fish of every type.
Sing the old Navy song on its base.
Visit all the islands from Mara.
Get all the Koa's backpacks.
Complete all the quests from Akaji.
Beat Ereti in a race.
Complete all the quests from Mayo.
Complete all the quests from Awan.
Complete all the quests from Onzo.
Complete all the quests from Noho.
Unlock all the crops on Home Island.
Get the boat to max level.
Sell objects for a total of 3000 coins.
Complete all the quests from Taka.
Complete all the quests from Brram.
Cook 50 dishes.
Get one farm animal of each type for your island.
Use the recycle bin 100 times.
Meet Dunna.
Craft 60 objects.
Sell objects for a total of 2000 coins.
Unlock the mine.
Sell objects for a total of 1000 coins.
Cook 30 dishes.
Carry 99 oranges in the backpack.
Craft 40 objects.
Read all the messages on Puni Cave.
Ask Caleb to take you back to Qälis.
Cook 15 dishes.
Meet Saimi.
Craft 20 objects.
Collect 90 objects.
Remember...
Collect 60 objects.
Wake up after the tutorial.
Collect 30 objects.