Adam, do some basic research, is google a mystery to you?
To land in inland waters you need the 'landowners' permission, no different to farm strips but more difficult to get.
If you think landing in the sea is smart - try to get some sensible info - yes it is possible - but it needs serious maintenance.
There are also serious operational difficulties in using coastal water and as for using a marina - very difficult is the best description.
Do some searching and gain some insight!