Sometimes you can explore farther inland. What looks to be an ocean can just be a very wide river mouth. Walking along the "coast" might allow you to find a place you can ford the river. When you are swimming you don't regenerate stamina but if there are boulders protruding from the water you can swim from boulder to boulder. Floating next to a boulder counts as wading and allows your stamina to regenerate.

With better materials found in tougher biomes its possible to build bridges from boulder to boulder and potentially cross a large river dry footed.