There are a couple of hazards that an ocean swimmer must be aware of: undertows, seapusses, drags, etc. However, finding consistent descriptions of these phenomena is quite difficult. These are the terms used in Long Island, NY, US. If you have other terms or different definitions, please let me know: firstname.lastname@example.org.
The ocean has rules. You must know what you are doing to swim in a rough ocean. This page is meant to help you understand the hazards and rules.
Here are my understandings of these terms: breakers, drag, riptide, sandbar, seapuss, set, swell, undertow, and washout.
Where the waves break. The breakers closest to the shore are called "shore break" or the first break. There can be a second break further out, especially if there is a sandbar. If it is really stormy, the waves are breaking as far out as one can see. Once you are "beyond the breakers" you do not have to dive or jump the waves; it is calmer. This is a good place to be when you are in trouble.
A sideways - parallel to shore - current.
a raised plateau a short distance off shore that causes the waves to break. This usually provide great waves.
ambiguous term - used for washout & undertow & monsters. I use it to refer to nearly harmless currents that float out to the first break. These are caused by water piling up on shore and needing to get back out. They seem to slide along with the drag. Do not fight them, swim sideways or just go with it until it dies out.
a set of waves - like ripples in a pond, waves often come in 2s, 3s, and 4s.
In Hawai'i, a swell is used to describe the ocean currents bringing in waves. As in there is a swell coming means there will be waves. On the East Coast it means the big ripple of a wave before it breaks.
When the shore break is large, lots of water keeps flowing in with the waves. That water escapes by flowing out, under the oncoming waves. The strategy is to get back to shore. The tactic is to jump up into oncoming whitewater of the waves and let them push you back into shore. If you get tired go out beyond the breakers and then pray and ride a wave back in.
The current flowing out between a break in the sandbar. A sandbar act as a slight dam, or weir for the water washing into shore. The water will flow out through a break in the bar. If you get trapped in a washout, swim sideways; do not fight the current. Once you are out of it, you can swim back to shore.