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5-acre lake near Gwynedd. The lake tops out around 23 ft. This chart interpolates between a real shoreline and a known maximum depth. It will point you at likely water, but it is not a navigation product. Every species below gets its seasonal read from the same numbers driving the chart.
Llyn Du maps at 5 acres behind 0.3 miles of shoreline. At index 1.1 the outline is almost a bowl — read the depth changes, not the shoreline. Roughly 56% of the water is 15 ft or less as modeled, the band where the food chain lives. It sits in Gwynedd. If the bite dies, Llyn Tecwyn Isaf is 5 mi to the southeast.
Spring puts brown trout in skinny water — 3 to 23 ft is the zone. Summer fish stay in 7 to 23 ft, and winter fish hold in 3 to 23 ft. Shoreline break is the standout, a drop-off at roughly 10 ft, rated prime for summer brown trout. Plan around after dark and early morning in the warm months. A spoon at the thermocline or a deep stickbait (night) covers the summer program.
Depth note: when a documented seasonal range extends below this chart, the table shows the deepest mapped working water, not a verified holding depth.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 23 ft chart-limited; documented 3 to 25 ft | dawn & dusk | Shoreline break (10 ft) | Stickbait off planer boards (shallow), Small spoon along mud lines |
| Summer | 7 to 23 ft chart-limited; documented 25 to 60 ft | night & dawn | Shoreline break (10 ft) | Spoon at the thermocline, Deep stickbait (night) |
| Fall | 4 to 23 ft chart-limited; documented 5 to 30 ft | dusk & dawn | Shoreline break (10 ft) | Jerkbait over gravel, Casting spoon |
| Winter | 3 to 23 ft chart-limited; documented 5 to 35 ft | dawn | Shoreline break (10 ft) | Jigging spoon, Small stickbait (slow) |
Early season european perch use the shallows, holding in 3 to 12 ft. Summer is a 7 to 23 ft game here, winter a 7 to 23 ft one. The chart's best answer is Shallow bay flat — weed flat, 3 ft, prime for spring. Best bite is early morning. Tie on a drop-shot micro plastics or a small crankbait (perch pattern) and you're in the game.
Depth note: when a documented seasonal range extends below this chart, the table shows the deepest mapped working water, not a verified holding depth.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Shallow bay flat (3 ft) | Small jig + curly tail, Inline spinner #1-2 |
| Summer | 7 to 23 ft chart-limited; documented 8 to 28 ft | dawn | Deep basin (20 ft) | Drop-shot micro plastics, Small crankbait (perch pattern) |
| Fall | 7 to 23 ft chart-limited; documented 10 to 33 ft | midday | Deep basin (20 ft) | Jigging spoon (small), Drop-shot on deep flats |
| Winter | 7 to 23 ft chart-limited; documented 12 to 33 ft | midday & dawn | Deep basin (20 ft) | Tungsten jig + maggots, Small balance jig |
Come spring, look for northern pike tight to the bank in 2 to 8 ft. They move out to 8 to 20 ft in summer and finish the year down in 5 to 15 ft. If you only fish one area, make it Shallow bay flat: a weed flat around 3 ft that scores prime in spring. Best bite is early morning and the evening. A bucktail or a weedless spoon over cabbage is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | Shallow bay flat (3 ft) | #5 inline spinner, Spoon (red/white) |
| Summer | 8 to 20 ft | dawn & dusk | Shoreline break (10 ft) | Bucktail, Weedless spoon over cabbage |
| Fall | 6 to 18 ft | midday & dawn | Shoreline break (10 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Shallow bay flat (3 ft) | Tip-ups, Large jigging spoon |
3 pieces of structure are mapped here — Deep basin, around 20 ft, is the deepest of them.
Llyn Du is about 23 ft (7 m) deep at its deepest point. The contours here are modeled from the water's real shape and maximum depth, so treat them as a rough guide.
Anglers target brown trout, european perch, northern pike on Llyn Du. This isn't a survey of the water — none is published for it — but an informed estimate from the species common to the region, narrowed by this water's depth, size and each species' range.
Shallow bay flat is the top-rated area: a weed flat in about 3 ft of water that rates prime for european perch in spring. Open the map above to see every rated spot for each species and season.
For brown trout, the summer bite is best in after dark and early morning. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.
Llyn Tecwyn Isaf 5 mi · Llynnau Cwm Silyn 6 mi · Llyn y Gader 6 mi · Llynnau Cwm Silyn 6 mi · Llyn Llagi 6 mi · Llyn Llenyrch 6 mi · Llyn Edno 8 mi · Llyn Gwynant 8 mi · Llyn Cwellyn 8 mi · Glaslyn 8 mi · Llyn Cwm Bychan 8 mi · Llyn Llydaw 9 mi
See how Llyn Du stacks up: best northern pike lakes in United Kingdom · best european perch lakes in United Kingdom · best brown trout lakes in United Kingdom
More water nearby: Gwynedd fishing maps (35 charts). Browse all United Kingdom fishing maps. See every water on DepthScout. How we build these maps. Fish here with a sonar unit that logs? Send us your depth data and we'll improve this chart, credited to you. For fishing guidance only, never navigation.