I've swum across the Delaware River and back at least once a year for the past 25 years. The spot I normally cross is about 400 feet across, on a relatively straight and calm segment of river. I am not a particularly strong swimmer or otherwise athletic. I just take my time and plug away. Some days I've swum back-and-forth twice, once three times. Sometimes I've worn a dry bag style day pack with lunch, hiking shoes, socks, shirt and a towel. But usually I just swim for the pleasure of swimming and come right back.

When the current is calm I aim for a rock directly across from where I enter the water, so I actually have to angle upstream to compensate for the current. But when the current is moving more swiftly I just swim perpendicular to shore and wind up wherever the current leaves me, walking upstream so my return trip puts me more or less at my starting point. But there are also times when the current was too strong to attempt, or once I got into the swifter water in the middle realized it was too strong and turned back.

There are several other spots on the river where the current is usually calm enough to swim across, and one spot where you can practically walk across the entire river, except for one short 50 foot channel. You need to study the current at different spots across the river. It can be calm 50 feet from shore then moving quickly in the center. Watch the debris float by, look for ripples in the water.

I've also swam and waded across the Raritan River and South Branch of the Raritan River in NJ. I got cocky on the South Branch and tried wading across just a few yards from a low damn. Got about mid-thigh and found myself stuck by the force of the water. Couldn't lift my foot to take a step without getting knocked over. Wound up going over the damn, fortunately only about 2' high, but got several bruises from the experience. I learned my lesson and give falls and damns a wide berth.