T-Rex: T-Rex presents The Periodic Table:
T-Rex: 33 ARSENIC
T-Rex: A toxic metalloid, used to create the chemical weapon Lewisite, 20,000 tons of which the USA stockpiled during World War II.
T-Rex: After the war the US treated it with bleach and dumped it all.
T-Rex: The Gulf of Mexico! True! Tons of arsenic dumped into the ocean!!
Utahraptor: Well, the ocean does have some arsenic in it.
T-Rex: Well it does NOW!
The author writes:
 About 1.6 parts per billion. Arsenic, Occurrence and Production, Wikipedia. This is actually well below the maximum allowable concentration in drinking water set by the US Environmental Protection Agency and Food and Drug Administration, which is 10 parts per billion. So as far as arsenic goes, sea water is perfectly safe to drink. The LD50 lethal dose of oral arsenic for mice is 145 mg/kg. To ingest this much arsenic, a 75 kg human would need to drink a little under 7000 tonnes of sea water. That's almost 3 Olympic-sized swimming pools full of sea water. So yeah, I reckon if you drank that you'd probably die of something other than arsenic poisoning first.