Information taken from the ACI website - discount on 2019 prices.

Sojourn tax lump sum has been reduced for boaters for 20% in 2020
According to this Regulation, boaters who paid the sojourn tax lump sum in 2019 for the period ending in 2020 are not required to pay the sojourn tax for the period that falls into 2020
If the period for which boaters paid the sojourn tax lump sum coincides with the period of COVID-19 Pandemic in the territory of the Republic of Croatia, the boaters can request either a pro-rata refund of the amount related to tourist tax they have paid for the period during which the declaration of the COVID-19 epidemic in the territory of the Republic of Croatia was in force, or they can request a proportionate extension of the time period for which the tourist tax has been paid. All requests for a refund or for the extension of the time period shall be submitted to the Croatian National Tourist Board
Example rates 2019 2020

9-11.99m up to 3 days 150,00 120,00
up to 8 days 350,00 280,00
up to 15 days 600,00 480,00
up to 30 days 1000,00 800,00
up to 90 days 2350,00 1880,00
up to 1 year 3000,00 2400,00