Negative Buoyancy, need help with my novel, about someone dying from drowning?

[Walternate]

Ok i'm writing a novel where my character tries to commits suicide by drowning himself. He ties his feet together, attaches weights to his ankles, tapes the rope so he can't untie himself and then jumps into the sea.

 

I need to know how much weight will my character need in order to successfully drown himself and stay at the bottom even if he struggles. He is using metal barbell plates.

 

How much weight will he need? Will 15kg (33lbs) be enough to keep him at the bottom? My character weighs 70kg (154lbs), he is 6 feet tall and not physically strong or good swimmer at all. (He couldn't carry the 15kg weights with his hands but used a backpack). The sea where he jumps is 30 feet deep.

 

 

I want to make it as realistic as possible.

 

thanks.

[CaptainPanic]

Keep him at the bottom for how long? Long enough to drown, or long enough to stay there forever?

When a human dies, you swell up. Gut bacteria will produce methane, and a body becomes a bit of a balloon. So, while you may initially sink, you can become buoyant even if you're dead for a while.

 

15 kg will certainly sink a normal person. Depending on body fat, and how much air he breathes in, much less (or no weight at all) might be sufficient.

To stay down, I have no clue. It's difficult to commit a perfect crime.

[swansont]

The human body is roughly neutrally buoyant once you exhale, but this depends on body composition. Fat is slightly less dense than water, while muscle is just a little more dense than water http://en.wikipedia.org/wiki/Adipose_tissue#Physical_properties

 

Having your lungs full will displace perhaps a few liters, so that's a few kg of extra buoyancy.

 

IOW, unless your protagonist is excessively obese (and 6', 154 lbs isn't), 15 kg should be sufficient to sink him.

[Walternate]

I see, thanks everyone . Just long enough to drown and die (5-10minutes).