Larger people pushed faster in current?

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BRT

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you aren't moving faster than the current, just at a higher proportion of the current speed than a less streamlined diver.

you reach an equilibrium between the normal force of the current against drag force to determine the steady state velocity.

maybe terminal velocity isnt the right term
So what creates the drag force? What are you dragging against? If you are not swimming or dragging on the bottom or something else you will rapidly reach water speed. It doesn't matter if you are a tiny piece of seaweed or a dead whale.
 

Lorenzoid

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. . . If you are not swimming or dragging on the bottom or something else you will rapidly reach water speed. It doesn't matter if you are a tiny piece of seaweed or a dead whale.

I think that's half the puzzle here: Even on a drift dive, most divers are finning, even if just a little bit so as to maintain a desired orientation. Divers in a group don't all reach equilibrium where they move exactly along with the current. At any given time, divers are likely to be moving at different speeds.
 

BRT

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there is form drag from your movement in the water itself.
Only if your speed is different than the water speed.
 

dumpsterDiver

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Obviously the diver's orientation, trim and size are irrelevant when the diver is passively drifting. As other have mentioned, position relative to the bottom is often very important. If you want to slow down, hug the bottom, figuratively or literally. If you want to "catch up' with the group, swim 10 feet off the bottom, get up in the water column where you will be less effected by the reduced velocity at the bottom.

One thing i can envision is that if diver A stops and holds onto the bottom (in a current) and when they release from the bottom, if they are facing into the current and are streamlined, they might give a kick or two into the current and their reduced drag might cause them to accelerate slower than diver B who leaves the bottom at a more aggressive angle of attack and then spins around quicker, since we normally don't drift backwards when drift diving. if there are a lot of starts and stops, I could see where it may appear that one diver is going to drift faster than another.
 
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runsongas

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Only if your speed is different than the water speed.

which it is. you won't perfectly match the water speed exactly and will still feel the movement of the current around you even during a passive drift.
 

BRT

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which it is. you won't perfectly match the water speed exactly and will still feel the movement of the current around you even during a passive drift.
You will if you maintain your buoyancy and quit kicking
 

TimAZ

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I also suspect it is true. My theory is smaller people are more streamlined (eg pointy) so a lot of the current that hits them is pushed over, under and around them. A larger person will have more cross-section to catch the current. I also note that in stronger currents, people with lots of gear (eg twin tanks, deco tanks etc) will have a harder job swimming into the current than a more streamlined person.
Heya Clownfish,

I don't know your experience level, but first, yeah, the larger the cross section you present to the current, the greater impact the current will have have upon you. That said, your control of your trim and relative position has a greater impact on your cross section than your physical size. As you improve in these, your physical size will get lost in the statistical noise in reference to other divers. Also, newer divers tend to fin whether they know it or not. A common practice is to stay a touch negative and fin gently to hold depth. This will both increase a diver's cross section and propel the diver forward. As neutral buoyancy approaches perfection, this goes away. Always practice and pay attention to neutral buoyancy. I still practice it every single dive I do. Not only will this help in the concern you have here, but it will help keep your fins off the reef. I'm sure you've seen folks churning across the reef like a roto-tiller. It sounds like you're talking about drift diving, maybe Cozumel. Pay attention to the terrain. A slight shift can drop you in the lee of a terrain feature and let everyone else catch up. Anyway, good question, I hope I helped, and have fun.

If you have any questions or concerns, feel free to PM me.

Also, NWgratefuldiver is an excellent resource, but don't tell him I said so.
 
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clownfishsydney

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Heya Clownfish,

I don't know your experience level,
Based on your details, I have a minimum of almost 3,000 more dives than you, so I do have a bit of experience. This has been in cold dark waters of northern Scotland and Norway to the tropical water of PNG, Chuuk and last week, the far north Great Barrier Reef. Last week we did quite a few drift dives, and the observation was again, that smaller divers were a bit slower than the larger ones, and we were not finning at all.

I am fully aware that a badly trimmed diver will be affected more by current. I am talking about properly trimmed divers of different sizes (and even gear configuration). Even going with a current, a smaller diver will be more streamlined than a bigger diver or one with lots of gear. If streamlined, then logic says that a lot of the waterflow will go around you, starting from your fins.
 

Pelagicsal

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if you are moving faster than the rest of the group during a drift, it is more likely due to you being more streamlined.
^^This statement is backward for drift diving. The less drag a diver has the better, when dealing with current. Being streamlined allows the diver, regardless of size, to better control his or her speed of movement along the reef.
 
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