Reserved skills? (not enough skill points)
 

When I try to upgrade my crew there's some skill with the words reserved. That make it looks like it'll unlock later on but it also says I don't have enough skill points to upgrade it (currently at 25, most skills cost 2...). Anyone know?

You have to sink some tonnage and go back to base to get points. Then you can upgrade the crew by clicking on the skill icon. If it's available and you have the points you may then apply. It may be that all skills are not available to upgrade even if you have points.

If you have No_magic_skills then some unrealistic skills have been locked out . The mega mod includes this mod apparently .

Ah damn... I don't see why training you crew to react faster is unrealistic, I wish I could remove the mega mod but my saved game crash when I do :(

General rule to be safe:

Install\remove mods when in base.

Most of the skills seem a bit far fetched, i.e. the all seeing sonar man who can apparently hear contacts outside the operating range of the sonar.