Expectation:

Entering any water will unlock the boat recipes.

"trigger": "minecraft:enter_block",
  "conditions": {
    "fluid": {
      "tag": "minecraft:water"
    }
  }
}

This is an impossible example because there is currently no way to check the fluid state of the entered block.

Reality:

Entering a water block will unlock the boat recipes, entering a waterlogged block will not.

"trigger": "minecraft:enter_block",
  "conditions": {
    "block": "minecraft:water"
  }
}