diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4142bf5c..62cc6c79 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ and uses [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 ## [1.1.2]
 ### Fixed
 * Renamed `hyp3_isce2.logging` to `hyp3_isce2.logger` to avoid shadowing built-in.
+* Source of product start times in `merge_tops_bursts` to use the `asf_search` umm record.
 
 ## [1.1.1]
 ### Fixed
diff --git a/src/hyp3_isce2/merge_tops_bursts.py b/src/hyp3_isce2/merge_tops_bursts.py
index ae71429c..f3ef8457 100644
--- a/src/hyp3_isce2/merge_tops_bursts.py
+++ b/src/hyp3_isce2/merge_tops_bursts.py
@@ -127,9 +127,9 @@ def get_burst_metadata(product_paths: Iterable[Path]) -> Iterable[BurstProduct]:
     burst_ids = [result.properties['burst']['relativeBurstID'] for result in results]
     burst_indexes = [result.properties['burst']['burstIndex'] for result in results]
     polarization = [result.properties['polarization'] for result in results]
-    start_utc = [
-        datetime.datetime.strptime(result.properties['startTime'], '%Y-%m-%dT%H:%M:%S.%fZ') for result in results
-    ]
+
+    start_utc_strs = [result.umm['TemporalExtent']['RangeDateTime']['BeginningDateTime'] for result in results]
+    start_utc = [datetime.datetime.strptime(utc, '%Y-%m-%dT%H:%M:%S.%fZ') for utc in start_utc_strs]
     relative_orbits = [result.properties['pathNumber'] for result in results]
     n_lines = [int(meta['Radarnlines']) for meta in metas]
     n_samples = [int(meta['Radarnsamples']) for meta in metas]
diff --git a/src/hyp3_isce2/water_mask.py b/src/hyp3_isce2/water_mask.py
index 489869e6..06681287 100644
--- a/src/hyp3_isce2/water_mask.py
+++ b/src/hyp3_isce2/water_mask.py
@@ -125,6 +125,7 @@ def create_water_mask(input_image: str, output_image: str, gdal_format='ISCE', t
         merged_warped_path,
         f'--outfile={output_image}',
         '--calc="numpy.abs((A.astype(numpy.int16) + 1) - 2)"',  # Change 1's to 0's and 0's to 1's.
-        f'--format={gdal_format}'
+        f'--format={gdal_format}',
+        '--overwrite',
     ]
     subprocess.run(flip_values_command, check=True)
diff --git a/tests/test_merge_tops_bursts.py b/tests/test_merge_tops_bursts.py
index 54ff6bb0..c2b8bfec 100644
--- a/tests/test_merge_tops_bursts.py
+++ b/tests/test_merge_tops_bursts.py
@@ -27,13 +27,15 @@ def mock_asf_search_results(
     path_number: int,
 ) -> asf_search.ASFSearchResults:
     product = asf_search.ASFProduct()
-    product.umm = {'InputGranules': [slc_name]}
+    product.umm = {
+        'InputGranules': [slc_name],
+        'TemporalExtent': {'RangeDateTime': {'BeginningDateTime': '2020-06-04T02:23:13.963847Z'}},
+    }
     product.properties.update(
         {
             'burst': {'subswath': subswath, 'burstIndex': burst_index, 'relativeBurstID': burst_id},
             'polarization': polarization,
             'url': f'https://foo.com/{slc_name}/baz.zip',
-            'startTime': '2020-06-04T02:23:13.963847Z',
             'pathNumber': path_number,
         }
     )