The first sea has a total of 14 main islands. If you’re a pirate you spawn at the “Pirate Starter” and if you a marine you spawn at “Marine Starter”. Both are for levels 1-24
List of Islands and level requirements.
Jungle: Level 15-30
Pirate Village: Level 30-60
Desert: Level 60-90
Middle Island: Level 100
Frozen Village: Level 90-120
Marine Fortress: Level 120-150
Skylands: Level 150-200
Prison: Level 190-275
Colosseum: Level 225-300
Magma Village: Level 300
Underwater City: Level 375-450
Upper Sky: 450-575
Fountain City: Level 625-700