Wind/Wave maxium for a fun dive? How is 12 knots?

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Granny Scuba

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I think there must be some type of correlation with winds and wave heights, but i dont really understand how wind relates to wave , etc etc etc.

What are the maxium wind/wave activity for a fun dive.

I just posted a similar but more specific (but not as techincal) question in the Florida forum.

thanks!
 
Hi Granny Scuba!

The answer depends on many things, most of all your comfort level.

What you'll probably find is that the water is a lot calmer just under the surface -- wave action usually doesn't translate very deep. IMO, if you can enter and exit safely, you can still have a fun dive in fairly high winds and waves. Entry and exit (boat? shore? helicopter?) will typically be where the greatest danger lurks.

PS -- The distance that wind blows over water = "fetch". The wave height is going to be a function of the fetch, wind speed, and time. That's the correlation you're thinking of.

Good question!
 
Here in Hawaii, the typical wind we feel daily does not really impact the typical dive sites, underwater. The "local" wind is predominantly from the North East; our "trade winds" are pretty much North North East to East North East. The North East sides of the Islands are called the windward sides, and there are almost no popular dive sites on the windward sides of the main Hawaiian Islands.

Hawaii is known for surfing waves, and those waves are produced by storm winds, typically storms over a thousand miles from Hawaii. Winter waves are produced by storms crossing the North Pacific from Russia to Alaska. Summer waves are produced by similar Souther Hemisphere winter storms crossing the South Pacific, way South of the Equator. Hawaii is much closer to the North Pacific storms so our biggest winter waves out of the North are bigger than our biggest summer waves out of the South.

We call the local wind waves, on the windward side, trade wind swell, and the far off storm wind waves, on the North, West and South shores, ground swell. Both swell types churn up the sandy beaches, making shore diving murky. Bigger ground swells even murk up deeper boat dive sites pretty far off shore.

Molokini and Lehua are mostly submerged ancient cinder cones with just a crescent of rock jutting above the surface of the ocean. The open side of each faces North, so I theorize that wave erosion shaped what we see, but there are undoubtably other theories. Neither of these Islands has much sand, so they are beautiful for diving even when there are significant swells.

Molokini is close to Maui, with West Maui and Molokai sort of blocking the winter swells and also sits in the wind shadow of 10,000 ft tall Haleakala, so it is beautiful diving nearly every day of the year. Lehua is significantly farther from Kauai, with no winter swell "blockers" and not really wind sheltered by 5,000 ft tall Waialeale, so the boat ride out is only scheduled ~4 months of the year. Lehua's underwater realm is likely at least as beautiful as Molokini, nearly as often, but divers don't get to go very often in the winter.

The Big Island (Hawaii) is the youngest Hawaiian Island, so it has a mostly igneous rocky shore line with very few sand beaches. That is the reason Hawaii's diving has the best average vis of the main Hawaiian Islands, and average vis goes down as you move older in age of Island, because the older the Island the higher percentage of sandy shoreline. Hawaii is also much better shore diving when big swells are pounding the Islands into their worst vis.

I have left out many details, probably need edits from other posters, and other regions of the world likely work differently. :idk:

Here is more reading....

Wind wave - Wikipedia, the free encyclopedia

NWS JetStream - Wind, Swell and Rouge Waves
 
Wind speed and wave heights are related, but "local" winds are only a part of what creates wave heights, so the correlation between wind speed and wave height isn't linear. Here is a nice, simple explanation from NOAA's National Data Buoy Center Science Education Page. You can get big waves even when it's not windy, so really, the thing you need to focus on is predicted wave height. The height of waves you are comfortable with is somewhat individual, but I personally am a wave wimp and prefer not to dive in big waves at all.

I live and work in a part of the world where there are seasonal monsoon winds. During monsoon season we get heavy seas so small boats with outboard motors simply cannot cope with them, and may even swamp. For this reason, most of our local dive boats are really big and can just power through the waves, even during monsoon season. The biggest issue I worry about among my divers when there is significant swell is getting back on the boat. If the boat is bobbing up and down a couple of meters, climbing a ladder can become a real issue. Our boats will always take us to the lee sides of the islands where we dive so that we are protected from the swell in order to prevent injuries. The other problem we face due to waves and swell is sea sickness. We always have motion sickness tablets that we hand out before we leave the safety of the harbor, and we really emphasize this on windy days!
 
Wind makes waves. Wave height and frequency affects your comfort level on the surface and getting on and off a boat. Not a big deal on shore dives, though surge may be. I think waves 3' and under are no big thing, have dove off a 36 foot boat in 15 foot seas, and it was a challenge, but worth it ( Hammerhead shark dive off the east end of Molokai). Dive within your limits, and within surface conditions you can handle both physically and mentally.
DivemasterDennis
 
The other consideration is that with waves comes surge ... which is the back and forth motion of the water as the wave passes by. In places like the Channel Islands, surge can be significant even at deeper depths ... 80 or 90 feet isn't uncommon to encounter surge that will rock you back and forth several feet. Surge is easy to dive in if there aren't any obstacles like rocks or kelp ... you just go with the flow. However, it can be disorienting, because your frame of reference is such that it feels like you're standing still and the whole world is swaying underneath you. I've known divers to get "seasick" because of it ...

... Bob (Grateful Diver)
 
Wind/wave max for a "fun" dive depends on your comfort level, as stated above.

Assuming you have no seasickness issues, the hardest part about waves/big seas is getting back on the boat. Depends on the kind of boat, but there's a skill and timing involved in grabbing a ladder, removing fins and climbing back on a boat in 10' seas! It can be fun though! I've never dived in 12 knot current, that's BRISK... I think before I did that I'd want to be very comfy with my buddy and our skills. 12kn is not something you can just swim against to get to a struggling buddy.

For a fun, no sweat, normal day of boat diving I'd say 3-5' max and 4-5kn max. I'd say above that it gets special... fun, but more careabouts/skill etc.

Just my personal assessment, others may be very different.
 
Everyone has a different comfort level and tolerance for sea conditions. The more diving and boating you do, the more you acclimate and are able to handle more variety of conditions. As for climate, it varies from area to area, to there are no hard or fast rules that universally apply. Just understand that basics, that wind pushes water. Waves and current are moving water.

When teaching, I typically try to keep it in the 2-4 ft or less seas. I seriously consider the physical condition of my students & their abilities for 3-5 ft or more seas. I personally will go out in 6-8 ft though being on the surface in that I know isn't much fun and understand the difficulty of re-boarding the boat I am on in those conditions.

In certain conditions I also sometimes take into account the size of boat (smaller boats rock more in rougher seas) as well as the ease of use of the ladders (each is a bit different) and the ability of the crew to assist me in rougher conditions. And then there is the number of divers - how long might I have to hang onto a tagline at the back of the boat before it is my turn to climb the ladder - on a calm day everyone can float easily while waiting, on a rougher day I've seen folks get queasy hanging around on the surface.

It's all a learning experience. With more time in the water, you will learn more skills for diving in differing conditions.
 
Wind/wave max for a "fun" dive depends on your comfort level, as stated above.

Assuming you have no seasickness issues, the hardest part about waves/big seas is getting back on the boat. Depends on the kind of boat, but there's a skill and timing involved in grabbing a ladder, removing fins and climbing back on a boat in 10' seas! It can be fun though! I've never dived in 12 knot current, that's BRISK... I think before I did that I'd want to be very comfy with my buddy and our skills. 12kn is not something you can just swim against to get to a struggling buddy.

For a fun, no sweat, normal day of boat diving I'd say 3-5' max and 4-5kn max. I'd say above that it gets special... fun, but more careabouts/skill etc.

Just my personal assessment, others may be very different.
Realistically, a 12-knot current is undiveable. I doubt you could even drift with it ... water moving that fast would tend to create whirlpools that could eat a boat, and a human simply wouldn't have the strength to do anything except get pulled along at the mercy of wherever it decided to take you. Swimming against, or even across, that kind of moving water wouldn't be possible.

4 to 5 knots is a very fast drift dive. I've only ever dived in current that fast once ... and all you can do is go with the flow and watch everything go by almost too fast for your brain to process. It's fun ... if you can relax and trust yourself to end the dive appropriately. But it's anything but relaxing.

Realistically, on scuba gear, you can't swim against more than about a knot of current for more than maybe a minute or two. My Sierra scooter can't even go against more than about 3 knots ... and a more powerful scooter like a 'Cuda would have a hard time against 5 knots ... if it could even manage to make headway.

Never underestimate the power of moving water ... it doesn't have to move all that fast to rock your world ...

... Bob (Grateful Diver)
 
I have found that, for offshore dives, it is not the wave height that is the biggest factor in how challenging a dive may be but the correlation between wave height and wave period. The closer together the two are, the steeper the face of the wave will be. 8 foot seas with a 20 second period are nothing but a ground swell and in many cases easily diveable, where a 4 foot wave height on a 4 second period will eat you alive. Try to get the most recent information from the buoy closest to your dive site and make the best decision possible by factoring in wave height and period, wind, and diver experience. A bad day on the water can be very ugly indeed and sometimes the best decision that can be made is to simply dive another day.
 
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