• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

Need a refresher

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

Spinal Tap

New Member
Jul 5, 2004
Need a Scuba refresher

I was certified about eight years ago and since then have only done about a half dozen dives. Since then I've only been freediving.

I recently bought a 19cu/ft pony bottle with regulator to use for unstucking anchors or cutting out fish that has wrapped too deep for me to freedive.

For this intended use, I'll only put the tank on to go down to cut kelp or loosen an anchor then come up slower than my bubbles. I don't expect my bottom time to exceed 2 minutes. I may go as deep as 90'. I don't believe I need any safety stops, correct?

Oh, I also won't be mixing the two (freediving, scuba). Once I retrieve the fish or anchor, I'm done.

Well, I've been thinking about the upcoming lobster season and I would like to use my new tank for some shallow water bug hunting. I've always just freedived for lobster and never to more than 40'. When scuba diving, what circumstances necessitate a safety stop? If I dive in 40' for 20 minutes, would I need to do a safety stop or can I ascend slower than my bubbles and be O.K?

Again, I won't be mixing the two. I'll either freedive for the lobsters or scuba. Even though my diving is shallow, I can't remember what the margin of safety was for doing both, so I'll only do one.

Last edited:
I would caution using a 19cuft pony bottle for dives as deep as 90' - have you figured how long 19cuft of air would actually last at that depth, including your ascent time and safety stop?

About safety stop - it's so called because it is not "required", but adds a margin of safety to the dive. Most dive tables will consider anything shallower than 20' to be in the safety stop zone (mainly because it's assumed that your body tissues will offgas nitrogen at about the same rate if not faster, than they ongas, at that depth). Therefore, a really really slow ascent (waaaay slower than your bubbles) after a ~20' dive could be a substitute for a "safety stop".
hi there - i would not advise using a pony bottle as a primary cylinder for scuba, and definitely not for going 90 ft deep.

a safety stop is simply precautionary and will ensure that the excess nitrogen your body absorbs at depth can come out in solution, because your body does not metabolize it. personally, i would advise hovering at 15 ft for at least 3 minutes (your safety stop) on any dive deeper than 50 ft.

it's always better to be safe than sorry, and when safely ascending you can never go too slow - go slower than the smallest slowest bubble you exhale.

if you go to 90 ft., whether it's for 2 minutes or 20, you NEED a safety stop.

have fun catching those bugs!

DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing


ISSN 1469-865X | Copyright © 1996 - 2024 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Ocean Advocacy and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.