On the bubble?

So, you are all welcome to laugh at my question. I have taken a lot of medications lately so rather than make mistakes I will just ask advice. How do I know what is level inside my boat so I can put the floor in correct? I know it wont be the perfect because of weight in the boat at any given time. Do I take it out on the lake, with a 4 foot level in hand and mark the insides of the boat or what? I cant go off the ridge that runs down the length of my boat because it drastically goes upward the more you move towards the front. Thanks for helping me!

Generally I would say to fill it up with water. The height of your deck should be the height of the water. If you level the gunwales, then level the water, you will have a level waterline. Keep in mind that once you have the first axis level (front to back), you need to keep it level while measuring the other axis (side to side). After each is level, draw a line at the water level.

Get what I'm saying?

Its all personal preference. I'd rather have it level with the floor personally.

I like both ideas. I looked at the boat in more detail today and I see the runner that runs right down the center of the bottom of the boat is perfectly straight until about 3 foot from the front of the boat. So, even measuring off the center of the boat on the inside up until that point should give me level location.
Any other ideas, I will gladly consider. Dont mean for such a simple thing to be a big deal, just wondering how guys have done it. Thanks