Thanks for answer udiprod!
I have managed to build a 9 tones tanker that can swim (with full capacity) at speed 12 m/s. :) Without an oil, it can go even 2x faster.
Also I have an issue about balancing S.O.S. message: if you are developing your ship and you don't want to sleep, eat and drink, just press SOS and go over it. Think about it.
And as far as I remember: big ships causes lags (consider some non-dynamic simplification). Also diving is a bit hard (diver suit idea). Plus some boxes for your staff (hard to implement?). And add some checks for diving near islands - some glitches happen there.
And I have a question about inventory: what is the correct limit: 10 or 99? I have spotted both.
One more bug helped me. SPOILER for new players!
Current version have a compass that cost 200 and you can sell it for 800. Please fix that.
Hope you will progress the game!