So I'm going to demonstrate how to do the boat pose. So you've probably done this in yoga. It's a pretty advanced ab exercise, so if you're not experienced I wouldn't just jump into it. I'd start out with some planks, maybe side planks, and then progress from here. If you have lower back issues, definitely be aware of that also when you're doing this pose.
So you want to make sure that your legs are coming up. Try to keep them straight. You're leaning slightly back. I like to say you want to lead with your sternum. So this is your sternum, your arms are slightly off the ground, and you're just holding this position. So I'm kind of on my sacrum, which is kind of like your tailbone, in the back. And you're just staying upward, like this. Notice how I'm shaking because my abs are working to engage the whole time. So your shoulders don't want to be rounded forward like this.
You want to be up, chest up. Sternum: lead with it. And make sure you're breathing easy. Start at 10 seconds and then progress from there. If 10 seconds is too difficult, start at 5. If that's too easy, then go for 30 and work your way up to 1 minute. And that's how you do a boat pose.