Go Eastward.

You turn east and run straight, headfirst into more thick jungle and and overgrowth. You run full speed, leaving behind whatever was running your way. You trip a few times and fall, scraping your knees some and putting dirt on them and your palms. You keep as straight as you can, as you run deeper and deeper into the unknown of the jungle. Soon you're out of breath, so you stop to calm down and think about your options.

Going back to the beach and the lusty-but-too-friendly mermaid is no longer an option. You look around and listen, taking in your surroundings. East should lead you back to the shore just away from where you had washed up. To your west you can hear the distinct crash and roar of a waterfall. Nothing seems to stand out going north but there may be something.