It had been snowing for days and the old ice was mostly covered with wet snow. At the same time wind and shipping had kept water open along the fairway. The ice to the left on the picture was 4-5cm thick while water wash had impregnated and hardened the snow on the old ice. The thinner ice is darker, while the old ice has more air bubbles and is less transparent. I followed the edge.
Another section on the same day was full of snow and water. Dry snow insulates the water and no icing occurs. You can see tracks from my footsteps. The tracks are full of water. The visible line is a crack in the ice, which has let seawater melt on the snowsheet from below.
Another spot of the same ice field is actually without ice or very weak. Perhaps only covered with snow. The crystals are different, more course. There are some dents and channels in the snow layer that say "water may have been sucked down the open drain hole" underneath. You can actually see two holes beside each other. That is an indication of a bigger area of weaker ice.
Where water and ice meets in the sunshine is the most enjoyable art of nature. I was on my way towards Hanko (Hangö). One short section had been blown apart and ice drifted to sea. I had to go ashore and quickly found consistent ice again.
If the ice forms during snowfall and with wind - soft spots may be formed and they would normally be humid and collect more drifting snow, that in turn isolates. I did stop here and poke with my poles in different places to learn about the ice. I concluded that the dark ice was ok and also readable. The wind prevented me from hearing the ice. I avoided the snow. Even the dark ice was still a bit soft with captured salt in it.