diff --git a/src/model/logbook.rs b/src/model/logbook.rs
index dad29e5..449ad30 100644
--- a/src/model/logbook.rs
+++ b/src/model/logbook.rs
@@ -62,6 +62,7 @@ pub enum LogbookCreateError {
     BoatLocked,
     BoatNotFound,
     TooManyRowers(usize, usize),
+    ShipmasterAlreadyOnWater,
 }
 
 impl Logbook {
@@ -144,6 +145,10 @@ impl Logbook {
         if boat.on_water(db).await {
             return Err(LogbookCreateError::BoatAlreadyOnWater);
         }
+        if (User::find_by_id(db, log.shipmaster as i32).await.unwrap()).on_water(db).await {
+            return Err(LogbookCreateError::BoatAlreadyOnWater);
+        }
+        
 
         if log.rower.len() > boat.amount_seats as usize - 1 {
             return Err(LogbookCreateError::TooManyRowers(
diff --git a/src/model/user.rs b/src/model/user.rs
index 7bc25ff..0079d50 100644
--- a/src/model/user.rs
+++ b/src/model/user.rs
@@ -93,6 +93,17 @@ WHERE name like ?
         .ok()
     }
 
+    pub async fn on_water(&self, db: &SqlitePool) -> bool {
+        sqlx::query!(
+            "SELECT * FROM logbook WHERE shipmaster=? AND arrival is null",
+            self.id
+        )
+        .fetch_optional(db)
+        .await
+        .unwrap()
+        .is_some()
+    }
+
     pub async fn all(db: &SqlitePool) -> Vec<Self> {
         sqlx::query_as!(
             User,
diff --git a/src/tera/log.rs b/src/tera/log.rs
index 71130e3..58df629 100644
--- a/src/tera/log.rs
+++ b/src/tera/log.rs
@@ -119,9 +119,11 @@ async fn create(
     {
         Ok(_) => Flash::success(Redirect::to("/log"), "Ausfahrt erfolgreich hinzugefügt"),
         Err(LogbookCreateError::BoatAlreadyOnWater) => Flash::error(Redirect::to("/log"), format!("Boot schon am Wasser")),
+        Err(LogbookCreateError::ShipmasterAlreadyOnWater) => Flash::error(Redirect::to("/log"), format!("Schiffsführer schon am Wasser")),
         Err(LogbookCreateError::BoatLocked) => Flash::error(Redirect::to("/log"), format!("Boot gesperrt")),
         Err(LogbookCreateError::BoatNotFound) => Flash::error(Redirect::to("/log"), format!("Boot gibt's ned")),
         Err(LogbookCreateError::TooManyRowers(expected, actual)) => Flash::error(Redirect::to("/log"), format!("Zu viele Ruderer (Boot fasst maximal {expected}, es wurden jedoch {actual} Ruderer ausgewählt)")),
+
     }
 }
 
@@ -135,6 +137,7 @@ async fn create_kiosk(db: &State<SqlitePool>, data: Form<LogToAdd>) -> Flash<Red
     {
         Ok(_) => Flash::success(Redirect::to("/log/kiosk"), "Ausfahrt erfolgreich hinzugefügt"),
         Err(LogbookCreateError::BoatAlreadyOnWater) => Flash::error(Redirect::to("/log/kiosk"), format!("Boot schon am Wasser")),
+        Err(LogbookCreateError::ShipmasterAlreadyOnWater) => Flash::error(Redirect::to("/log"), format!("Schiffsführer schon am Wasser")),
         Err(LogbookCreateError::BoatLocked) => Flash::error(Redirect::to("/log/kiosk"), format!("Boot gesperrt")),
         Err(LogbookCreateError::BoatNotFound) => Flash::error(Redirect::to("/log/kiosk"), format!("Boot gibt's ned")),
         Err(LogbookCreateError::TooManyRowers(expected, actual)) => Flash::error(Redirect::to("/log/kiosk"), format!("Zu viele Ruderer (Boot fasst maximal {expected}, es wurden jedoch {actual} Ruderer ausgewählt)")),