Buoyancy of OpenROV in spearfishing project and activating the trigger remotely


Hi all,
We are preparing for the spearfishing project …

and so far, the aspects we have thought of in what we are trying to do are:

  1. buoyancy affect; of course we don’t want to change the neutral buoyancy since we will add the weight of the gun to the ROV.

my question is what things can we do to the ROV to make it handle more weight ?
Is it just by adding flotation ? or there is something that we can change in the hardware of the ROV ?

I thought about adding more motors , because the speed will be affected ,
how many extra motors can I add ?

  1. also I’m thinking about how to activate the trigger of the gun remotely; Any suggestions ?


Here’s a suggestion. Become vegan.
The oceans are already over-fished, we have ravaged them for our own needs. Why on earth are you devising even more ways of killing a dwindling ecology.
I believe the spirit of OpenROV is exploration, seeking to look for ways to make amends for the havoc mankind has wreaked on the environment. You do what you want, but it looks pretty sick to me.


It’s just a senior project we don’t want it to work for the sake of real fishing .

We want to apply some of our theoritcal background and I like this idea. And then we can cgange the application if we succeeded in this challenge.

however fishing will always be a source of food for humnas XD
But in my opinion methods as Nets and hooks is better if fish can be hunted by them. Spears shouldn’t be used unless it is necessary.

Anyway thank you for your opinion!

Best wishes


There are ballast weights (2x3oz on the 2.8) that can be removed. If I remember correctly from previous posts this is not going to be enough so you will need to displace more water (flotation is probably the easiest way).

If you do a little searching on the forum you can find other motor configurations people have used. I think the highest number so far is 6 motors total. You will have to do hardware, electronics, and software modifications.


Hi @Brian_Grau ,

So the OpenRov is designed with extra ballast of 3oz, to make it neutrally buoyant and this ballast is removable?
Is that what you meant?


There are two 3oz weights (one on each side) for a total of 6oz of extra weight. This ballast is removable.


@Brian_Grau thank you :+1:t3::+1:t3:


So long as the ROV is
-Neutrally buoyant (weight in water= buoyancy)
-Center of Buoyancy is higher than Center of Gravity
-You do not greatly change drag
then the ROV will still work.

Assuming the speargun is heavy in water, I Suggest you attach it to the bottom of the ROV to lower the center of gravity.

Then I would add buoyancy to the top of the ROV. Need to use pressure-rated closed PVC Foam or could use pvc pipe capped on the ends.

We added foam to the top of our ROV and ballast to the bottom to increase its stability.

Hope this works