What do you consider bad diving conditions (in terms of wave height, swell, and period)?

[charlier]

In SE Asia, Force 4 is questionable, but possible. I guess it depends on the weather pattern and wind trend, and location of boat/dive site. I have seen squalls rapidly develop from force 4 to force 6. At this point, I'd wait it out and after say an hour or so, I might have want to head home (South China Sea to Singapore). If the wind is blowing the tops of the waves off, with lots of spray, it's hard to safely pick up divers using a RIB or safely climb a ladder.

 

[jonhall]

What do you guys consider bad conditions in terms of wave height, swell and period?

For me, 6-8 foot swells, regardless of the period, are bad conditions. Had never gotten sick on a boat until one fateful day in 2009. It's especially not fun when you know you're going to dive again the next day in similar conditions. To this day, unless I forget, I take motion sickness meds, whether I need them or not, before going out on a boat. Haven't been sick since.

 

[clownfishsydney]

Depends if you are talkin gabout shore diving or boat diving.

Shore diving, also depends if going in off a beach or rocks. Lot easier off rocks in a small swell than off a beach.

For boat diving, as a boat owner, my main limitation is wind speed and direction. Any wind over 15 knots from south in Sydney means I will cancel. 15 knots from west is okay as offshore. 15 from north not too bad and 15 from north-east can be bad, but depends. This is because these winds will make it so uncomfortable and also after a few hours of these winds blowing, dangerous.

As to period, I disagree with most of what has been posted earlier. Period is very important. You can have a small swell (say 1 metre) but with a long period have a very uncomfortable dive. Wave period is not really related to swell height. For example,

Wave Period Between waves Wave Speed Depth of surge
Seconds Metres Km/h Metres
8 100 45 16
10 156 56 25
12 225 67 36
14 306 79 49
15 351 84 56

As you can see, if you have a wave period of 8 seconds you will have surge (just) at 16 metres. But a long surge of 12 seconds will go to 36 metres and 15 seconds to 56 metres. This is not dependent on swell height.

Therefore, for boat diving, a combination of wind speed and direction, swell and wave height and wave period will determine if the dive is safe (and comfortable).

Even after almost 30 years of boat and shore diving, I still get it wrong sometimes based on the forecast, so it is not an exact science. However, I will say that in the past 10 years with all the electronic weather information available, we have very few days when we go out that we have to turn around and come home without diving.

 

[Skeptic14]

There's safe and then there is enjoyable too.

The conditions might not be dangerous but will the dives be enjoyable? Will the boat ride be tolerable? Will the shore entry/exit be frustrating or exhausting?

I'm fortunate to not get motion sick but I've seen many divers spend the 4+ hrs on a boat looking miserable and probably wishing they weren't there.

 

[100days-a-year]

I look at wind speed too,a big swell can get super ugly quick if the wind picks up a little bit.

I've dove in rolling 6-9 foot seas commercially and I'm in very athletic shape,getting back on the boat is more than most people can manage.I won't ask novices to go if it's more than 3-5'.

 

[RyanT]

In part it depends on the boat. Years ago when I dove off my buddy's 23' boat in the Gulf of Mexico, 4' was pretty much the max we'd do. Even at that, it made for a pretty uncomfortable day. My current buddy and I recently dove off a 65' boat in 4 to 6' seas. Getting back on board was a little bit of a challenge, but nothing scary. We did feel a little beat up by the end of the trip though. I did have to get back on a boat in 6-9' seas once and I found that to be a really frightening experience. At times the entire ladder and dive platform would come out of the water while you were trying to time your moment to grab the ladder. I hope not to do that again. So for a decent sized boat, I'd say that 4-6' is my absolute upper limit and 3-5' still makes for a rough day.

 

[stuartv]

It depends on the boat and the location. 5' seas off NC on a big boat is doable. 5' seas off Pensacola from a 6-pack sized boat is not so doable.

In Kona, 2' seas meant no diving. There, the diving is very close to shore (compared to, say, NC) because the bottom slopes away from the island so steeply. That close to shore, 2' seas means brutal surge when you're on the bottom in 30 to 40 feet of water.

 

[TMHeimer]

There's safe and then there is enjoyable too.

The conditions might not be dangerous but will the dives be enjoyable? Will the boat ride be tolerable? Will the shore entry/exit be frustrating or exhausting?

I'm fortunate to not get motion sick but I've seen many divers spend the 4+ hrs on a boat looking miserable and probably wishing they weren't there.

Good point. I've had some less than enjoyable shore dives farting around with entries/exits/viz. I still tend to do them if I deem them "safe". That old "Well, I did all the work, travel to get here" thing.

 

[tursiops]

The wind generates the waves; the waves can travel long distances and no longer be driven by the local winds. As the waves propagate, the shorter-period wave dissipate until only the longer-period waves still exist. That is swell, it was generated somewhere else and has propagated to your location. It may be going a direction quite different that that of the local wind-generated waves. For waves in deep water, longer period means longer crest-to-crest distance, and it is that "wavelength" of the wave that is all-important to us diving, because the fall-off in wave energy with depth is much less for a long-period wave than for a short-period wave. Swell produces more surge near the bottom, more silt/sand stirred up.
Really short period waves can be nasty to deal with if you are entering/exiting the water; things change in just a few seconds.

Local wind waves have periods from a few seconds up to maybe 6-7 secs. Swell tends to be 8+ seconds, and is usually quite low rollers, gently coming in, making the diving uncomfortable but much easier to deal with on entries/exits (to a boat).

A lot of captains worry mainly about the local wind-driven seas, because they can really affect the safety of the divers. Hence, they tend to grade things by the winds speed and how long it has been blowing....because the waves can keep growing if the wind keeps blowing.

 

[rhwestfall]

This past summer, we went from our home waters (Lake Erie) over to Lake Ontario to do some diving. Winds were a little weird on this trip, and we ended up with 1m waves and a 1-2 second wave period. Captain was all grumpy and was talking about calling it as it was mean for deep Lake Ontario. After telling him that this is what we get in Lake Erie (much shallower than Ontario), he took us. Boat slammed and crashed constantly, the captain repeatedly cursed, suiting up was like being in a rodeo, and the boarding ladder was quite the challenge to get back on, but the diving was spectacular. It's what we expect.....

It's quite a ride when you are on the bottom rung of the ladder, and 3-4 feet out of the water. That is when you finally understand why you were taught to keep your regulator in your mouth until seated on your seat.....