From a new game, take with you the emetic grenade from the 'Merle Revelation escalation (https://www.youtube.com/watch?v=FPl65.
..) and a lockpick.
You will get the story mission 'A lucrative opportunity' along with a bunch of challenges.
I get the tricky stuff out of the way first and then go for the easier kills after. I should have got the story mission 'The water horse', but didn't for some reason...
You could drop the coconuts on the target, but the boomerang starfish is far more entertaining!
For the Silent assassin with a Sniper rifle on Master difficulty challenges/achievements.
Take with you your best sniper rifle stashed in your hut and bring along your lock pick and emetic grenade from the Merle revelation escalation (https://www.youtube.com/watch?v=jjyvd.
..). Start in your hut (Shark) for convenience.... And an achievement!
I started with the tricky stuff first, aiming for the following story missions-
Take a deep breath.
The shape changer.
The water horse.
I did not get the 'water horse' again. You trigger it by eavesdropping the people on the beach and then retrieving the key. I think he got poisoned before the mission triggered... Best laid plans eh!
I made a save at the end as this is a good disguise for getting the hidden achievements that I will upload soon.