Indian Swimming Advice

It's a hot day and the traveler comes to a river inlet where an Indian is sitting on the bank.
The traveler asks,
Are there any stingrays here?
No stingrays.

So the traveler strips off his clothes and dives in.

After a while he yells a question to the Indian,
It's a hot day and the water's cool. Why aren't you swimming?

Too many electric eels, says the Indian.