“A'ight, so you wanna hustle? This is your hustle - the Lost and the Vagos is having a meeting of minds down in the LS River. It'd suit my purposes if they got stuck up. Light'em up, bring whatever they holding to the crib, you gonna make some bills. Straight up.”
The Vagos and the Lost are having a drug-dealing meeting over the LS River. Gerald wants that the team to hold everything that the both gangs are keeping (mostly methamphetamine) and bring the drugs back to Gerald. The deal takes place in a construction site near the river. Once all the gangsters are dead, one of the players needs to take the stuff and get back to Gerald's apartment.
Steal the meth.
Deliver the meth to Gerald's apartment.
GTA Online - Mission - Flood in the LS River Hard Difficulty