I think there's a possibility of the term "rip" being used here in two quite different contexts.
One (which Astrid's post refers to) is the sort of rip caused essentially by wave action, which happens at surf beaches, because of a strange thing about breaking waves.
The water in a normal wave doesn't actually go anywhere. It's like tying one end of a rope
to a wall and waving the other end up and down: waves travel along the rope
but the rope stays put. (Individual bits of rope actually orbit around in circles, looked at side on). Similarly the bits of water in an ordinary wave don't, over time, travel anywhere (unless there's an underlying current from some other cause)
However when waves get steep enough on the fronts for them to break forwards (which incidentally almost NEVER happens offshore) things change, because that water has escaped from the recirculating energy system of the wave, and is now tumbling, under freefall (impelled by gravity) down a steep ramp
which itself is moving (not the underlying water, but the 'geometry' of the water) towards the beach.
So at a surf beach all this extra water gets transported inshore, about mean sea level, and as we know, water tends to find its own level, so it has to get back out somehow. It does so in rips.
This sort of rip is not CAUSED by tidal flows, but it does vary in intensity with the state of the tide, because the underwater trenches through which these rips are channelled are sometimes almost the only viable route
, depending on how deep the water is around them. And naturally this 'landscape' varies with the state or height of the tide. So, rather confusingly, these rips sometimes get called tide rips, but really they're wave action rips.
Another sort of 'rip' is caused by a tidal current (caused by the difference in the height of tide between different adjacent bodies of water, or parts
of a single
such body) being intensified locally by channels and other aspects of the underwater landscape. (Such as sudden changes in depth
, causing upwellings and suchlike)
This can cause strange phenomena when ocean waves are travelling in the opposite direction. On very special occasions at certain locations it's possible to get standing waves tall enough that any ordinary vessel would simply run out of thrust and momentum trying to get up them.
Standing waves are a cute inversion of what I just said about ocean waves.
In a standing wave, it's the geometry which is going nowhere, whereas the bits of water are very definitely travelling at speed (due to the tidal current). Luckily these are remarkably rare (except in white water rivers), and there's almost always another way around them, or (because they're almost always a tidal phenomenon) you just heave to and wait a few hours.
But I'm sure what's being talked about in your case is something much less daunting. Any narrow passage
will have strongish rips within it (local 'streams' of strong flow, sometimes rotary eddies and even turntables - we don't talk about 'whirlpools' because it frightens suggestible children) at certain stages of the tide, and often you can cheat (if you're travelling against the flow) by hugging one shore or other, where there is often a 'back eddy' travelling in the opposite direction. Unless the maximum flow is over six knots or so (or there are tricky rocks which are not easily seen) you don't usually have to be ultra conservative, eg check fuel
filters, seal all open hatches etc etc.
I hope I haven't confused the issue, but you have to at least be clear that there are two very different phenomena with the same name.
Occasionally you strike a venue where both sorts of rip are happening, and river or harbour bars are an example. Unless they're very benevolent, I think it's prudent to steer clear of them until you've had lots of experience of each phenomenon in isolation from the other.