Using 10 stop ND Filter, need tutorial/help

[ivans75]

Hey guys, bought a zomei 10 stop ND filter (100mmx100mm with 82mm holder), and I have been using it twice at my local beach so far and I am not really happy with what I am getting so far. So any tips in regards to:
-what time of day is better to shoot with ND filter
-wheather condition (clouds? gray sky? blue sky?)
-apperture (which apperture for which light condition)
-general tutorial
are greatly appreciated..

Here's what I have done so far learning from youtube and reading from some blogs:

Set my camera in B mode
Have my apperture on 10-13 (tried 22)
auto focus before I put the filter on
Trying results in 3.5,8,12,15,30,45,60,70 seconds

Here is the sample i took in frankston this after with exif data, i dont really like the result
unedited by Ivan Sutrisno, on Flickr

Exif as follow
File Name IMG_1596.CR2
File Size 26.0MB
Camera Model Canon EOS 80D
Firmware Firmware Version 1.0.2
Shooting Date/Time 28/08/2017 11:39:24 AM
Author Ivan Sutrisno
Owner's Name
Shooting Mode Bulb
Tv(Shutter Speed) 15.3
Av(Aperture Value) 22
Metering Mode Evaluative Metering
ISO Speed 100
Auto ISO Speed OFF
Lens EF16-35mm f/2.8L II USM
Focal Length 16.0mm
Image Size 6000x4000
Crop/aspect ratio 3:2
Image Quality RAW
Flash Off
FE lock OFF
White Balance Mode Daylight
AF Mode Manual focusing
Picture Style Neutral
Sharpness:Strength 0
Sharpness:Fineness 2
Sharpness:Threshold 2
Contrast 0
Saturation 0
Color tone 0
Color Space sRGB
Long exposure noise reduction Disable
High ISO speed noise reduction Disable
Highlight tone priority Disable
Auto Lighting Optimizer Disable
Peripheral illumination correction Disable
Chromatic aberration correction Disable
Distortion correction Disable
Dust Delete Data No
Drive Mode Single shooting
Live View Shooting OFF
Camera Body No. 185023001424
Comment

this is edited version,
edited by Ivan Sutrisno, on Flickr

There is a white streak on the right, is that light leak? I thought it was a light leak and caused by the cheap filter i am using but I ve read same leak problem with lee big stopper too.
Shot this with remote by the way.
Thanks in advance

- - - Updated - - -

by the way, i did not take this pic with a tripod as i forgot to bring it with me. instead I placed the camera on a stone like retainer along the beach line, it is flat and somewhat high enough to see a bit of water. Higher position with tripod may look better.