Diving from an inflatable: choosing the spot, the seabed and a day with clear water
Diving from a small inflatable is one of the best reasons to own one, and it is also where not having a depth sounder shows most. There are three questions worth answering before you get in: how much water is there, what is underneath and whether you will see anything. And a fourth, the important one: whether the boat stays put while you are down.
A case: two coves, one Saturday and a decision
Example scenario.
Dani and a friend want to snorkel and do some freediving. At home they look at the chart in Embarca and mark two spots with a depth contour of about 6 to 8 metres close to shore, and a rocky area that promises fish. They check the forecast: on Saturday an easterly swell comes in and the more exposed spot will have stirred-up water; the other one is sheltered. They pick the second. On site, before dropping the anchor, they check the bottom by eye and with a lead line: sand next to the rock, good holding. One stays on board, the dive flag in the water. None of this required a depth sounder.
1. Depth: what you need it for
For diving, depth decides two things: how much line you let out to anchor (explained in where to anchor without a depth sounder) and which dive is reasonable for your level. Embarca's depth is a chart estimate, with cells of 115 to 460 metres: good for choosing candidates, not for planning a dive. If you dive with a tank, you measure the real depth yourself, in the water.
2. The bottom: rock, sand and meadows
- Rock is what usually brings life (and fish): crevices, caves, fish. It is also the worst thing to anchor on, because the anchor snags or does not hold. Ideally you anchor in sand near the rock, not on top of it.
- Posidonia meadows (the dark patches on sand) are a protected habitat, and anchoring on them is penalised in many places. Check the rule for your area and look for a clear patch of sand.
- Shoals and submerged rocks show on the chart as crosses and asterisks. Learn to spot them in how to read a nautical chart. And remember a data cell can hide one that does not appear.
3. Water clarity: what spoils it
Clarity cannot be guaranteed from home, but there are reasonable clues (general rules, not measurements):
- Recent swell. A long swell stirs up sand and silt from the bottom, especially in shallow water. After several days of rough weather the water usually takes a while to clear.
- Heavy rain and rivers. They wash down mud and release it near river mouths and dry riverbeds. After a storm, stay away from them.
- Wind from land or from the sea. A shore exposed to wind and waves clouds up sooner than a sheltered one.
- Spring. It tends to bring more plankton and less transparent water. And fine sand bottoms rise with a simple fin stroke.
- Light. With a high sun you see more than under an overcast sky or early in the morning.
What Embarca does not do today is calculate water visibility. If that matters most to you, there is an app, Spearo, made for it (we compare them in the comparison). What Embarca does give you, with Pro, is wind, gusts, wave height and period hour by hour, which explain a good part of why a day is clear or murky; and how to read levante and poniente helps you pick the sheltered side of the coast.
4. While you are down
The boat anchored with generous line, the engine off and someone on board watching it. A boat that drags with people in the water is one of the typical summer emergencies.
- Signal your presence with a regulation buoy or marker. Other boats must keep at least 25 metres clear around it.
- Spearfishing is banned in bathing areas.
- Tell someone your plan and your time back (how to tell someone your return time).
- Never dive alone. And if you see dolphins, remember you do not swim or dive with them within 60 metres.
Free and Pro
Estimated depth and the detailed chart of Spain are free; the seven-day forecast with its windows is Pro. The Pro trial lasts 3 outings. Full table on the home page.
Sources
- Salvamento Marítimo, underwater activities (signalling, 25 m clearance). Checked on 14 October 2026.
- Law 42/2007 on Natural Heritage and Biodiversity (BOE). Some regions and protected areas have their own rules on anchoring and posidonia: check them.