What occurred was water aspiration, apparently deep enough or in sufficient volume penetrating the dog's lung field to shut down gas exchange partially. The owner should continue to monitor the dog to make sure no stomach fluids made it into his lungs or trachea(probably didn't happen, but be careful) which, since these would contain gastric acid would be very low pH and possibly induce tissue damage. The other issue with aspirated stomach fluids is that they can induce aspiration pneumonia due to the bacterial load that "go along for the ride". I have no idea how clean the water you were clamming in was, but it was high saline content and likely had significant bacterial loads, some of them potentially pathogens.

Water intoxication is a condition where body fluids become so diluted by water volume ingested that electrolyte concentrations fall markedly, altering diffusion rates and osmosis impacted nutrient dispersal into tissues. This outcome would require the dog to drink a very large volume of water. In high saline conditions, the dog would likely puke well prior water intoxication onset due to the high "osmotic load" incurred.