Welcome to the sailing world!
Teak lasts a lot longer than that boat is old. I have teak railing (not decking) that is 35 years old and still looking great. Your problem, it seems, is that the previous owner didn't take great care of it.
Drying the decking out and re-caulking things is a weekend's worth of work, at the least, but a very do-able DIY job. This and re-sealing the teak (or leaving it the natural grey) will hopefully leave you happy.
Now if the water
is in the fiberglass
of the boat, the problem is bigger. A survey
this problem out. (Look for mushy deck
spots near where the deck
is penetrated by hardware
or chain plates. In the middle of a flat area where the teak deck
generally is would be unlikely.)
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