{% set depth = states('sensor.airmar_depth') | float %}
{% if depth < 3 %}
  {% set ratio = 7 %}
{% elif depth < 5 %}
  {% set ratio = 5 %}
{% elif depth < 7 %}
  {% set ratio = 4 %}
{% elif depth < 10 %}
  {% set ratio = 3.5 %}
{% else %}
  {% set ratio = 3 %}
{% endif %}
{% set chain_length = depth * ratio %}
{% set final_value = chain_length if chain_length >= 15 else 15 %}
{{ final_value | round(0, 'ceil') }}