The Giant Sea Snake is encountered at the end of the Royal Trouble quest. It is not as strong as its combat level suggests, but an antipoison potion, preferably super, is vital, as the snake is poisonous with damage that starts at 9. It fights with melee up close and ranged from a distance, but it cannot detect the use of prayers. Like its offspring, it is vulnerable to Magic. It drops the heavy box which is needed to finish the quest, and it can only be fought once.
Level 40 Slayer is required to kill this creature. (Note: This may be an unintended bug, but if you have been assigned a Dagannoth task, defeating the Giant Sea Snake currently counts as a kill)
The best way to defeat the snake is to attack it from afar with magic to exploit its weakness. Players can freely use Protect from Missiles to reduce all the damage besides poison. Other factors such as what food to bring and what armour and weapon to use are left to the player's decision. It is recommended to bring at least lobsters or swordfish. A dwarf multicannon can be setup in this area.
The following drop rates are provided by Jagex, unless otherwise specified.
The average Giant Sea Snake kill is worth 471.4.
There is a 5/128 chance of rolling the herb drop table.
There is a 14/128 chance of rolling the uncommon seed drop table.
|Snape grass seed||1||1/239.5||1,713||56|
|Poison ivy seed||1||1/737.1||16||99|
|Potato cactus seed||1||1/1,197.7||15||84|
|Dwarf weed seed||1||1/4,790.9||108||3|