What are you looking for, and what do you need? What plans do you have for that floating deck?

The deck looks pretty useless in size so why not first decide what that is going to be used for , then make it the size needed for that purpose. The rest we need a ton of info as to what you would want for the yard. Do you have kids ? Do you entertain outside ? So much missing info. Do you own the house ?

What is "good use"? Make it prettier? Plant some ferns. If you're in New England and that's Eastern White Pine, you might be able to get some Lady Slippers to grow.

I think your floating deck is too kind of small to put table with chairs on.

Some ideas

or place grill on the deck