On the "Join Project" page, scroll to the "Other". You will see three options about sharing the exact location of your seahorse sightings.
Please choose Option 2: “Yes, no matter who adds the observation to the project.” Exact locations are important for science and this option allows the project curator to add your seahorse sightings to iSeahorse in case you accidentally forget to select ‘Project iSeahorse’ when uploading your observations.