Seawater is many times more salty than the "pinch" of salt that is often recommended to add to cooked dishes.
According to the USGS
the concentration of salt in seawater (salinity) is about 35 parts per thousand. In other words, about 35 of 1,000 (3.5%) of the weight of seawater comes from the dissolved salts
To translate that to a typical glass of water: seawater is equivalent to adding a bit more than an entire tablespoon (17.5 mL) of salt to a 16oz (~500 mL) glass!
By the way, 1 tablespoon of salt is about 7100 mg. To put that into perspective, you'd have to consume almost two entire 8-cut pizzas (using Domino's as a reference) or more than 7 McDonald BigMac cheeseburgers to consume that same amount of salt.
In fact, consuming 7,100 mg of salt would more than triple the recommended amount for daily intake. According to the FDA:
Americans eat on average about 3,400 mg of sodium per day. However, the Dietary Guidelines for Americans recommends limiting sodium intake to less than 2,300 mg per day—that’s equal to about 1 teaspoon of salt!