I have stayed at hotel marina a number of times when visiting penzberg on business, the hotel it is about 10 minutes walk to the local train station or 2 mins in a taxi.
The hotel rooms seem to vary but all have been comfortable with large beds and balconies and all of a good quality. The majority of them with a view of the lake. Depending on the building the room style will change, for example you could have a huge room with a four poster bed and vintage furniture, and another time a slightly smaller room with more modern fitting. This doesn't seem to have anything to do with how much you pay.
The hotel restaurant is of a good standard, it has a limited core menu and changes its specials board monthly. The food has always been cooked very well however when staying for a week you soon run our of new things try.
The pool and sauna are nice and of a good size. Staff are friendly.
Overall this is a great hotel with a nice feel to it. very relaxing and I recommend to anyone wanting to see this part of germany.